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W. Tripp

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Everything posted by W. Tripp

  1. Project 280+P (Part I)

    Part I Introduction: This is a basic build up of a Mercury 2.5L 280 horsepower engine for a lake use STV River Rocket. This build up is based on real world requirements and expectations for use on pump fuels. It is not a race engine, but it may be used for occasional informal racing in a heads up style. As a firearms enthusiast, I chose the name of the project based on my relationship with reloading cartridges. A cartridge load that is significantly more powerful than normal over the counter loads is termed +P for added power. This term seemed appropriate for this project. This is a basic performance build, not a racing project. More power can be made, and more efficiency can be gained. But this project takes an approach that is based on goals for how I use my STV and what I wanted THIS engine to achieve while being easy to reproduce by others. In many places I have assumed the reader has a given understanding of these engines, how they operate, and basic performance and engine terms. If something is not clear, PLEASE ask questions, and I will answer as best I can. I am not a professional engine builder. I am not an outboard GURU. I am an enthusiast with a good amount of experience racing and running performance outboard powered boats. This project reflects these points and many other enthusiasts should find it informative and interesting. I do not expect everyone to need or want the limitations and goals of this engine project. I dont even expect everyone to agree with the way this engine is built. This is simply the way this engine was built. Take it as it is a fun project. Background: The Mercury 280 engines became available in 1999 as a replacement for the 260 hp engines previously available to consumers through the Mercury Racing product line of outboards. These engines have proven to be reliable while offering good performance in an outboard marine engine. Many of these engines now have a large amount of time and use on them. As a result, many are in need of rebuilding and many of their owners would probably like to see what is involved in getting more from their engines in place of a simple rebuild. Up until the release of the Drag engines in mid 1995 (as 1996 models), the 260 was the most powerful engine available in the Mercury Racing line of outboard engines. It was a hand ground block in which nearly each year the port specs changed, and the offshore race engines tended to be the best of the bunch. The Drag block is a new design and the 280 engines are based on this engine, with 150-160 psi compression using o-ring heads (a bit more than the 260 engines), and slightly lower port timing than the best 260 engines and significantly less than the Drag engines. Situation: The 280 engines make peak power at around 8000-8200 rpm with around 286-289 crankshaft HP. [This compares reasonably with the 260 engines, but the power is slightly increased and broader.] Compare this to the Drag engines with more power (335-ish hp) at 8400-8600 rpm. The late model Drag engine uses a single ring piston for less drag (about 5 hp at peak) but more blow-by, resulting in less power below 6500 rpm, and a reduced ring life, compared to the dual rings per piston on the 280 engines. The block is nearly the same as the Drag block, and is cast in the same molds. The major difference is the port timing and the roof of the exhaust ports. The exhaust port roof has a longer roof that turns downward in the exhaust chest. This longer, down turned, roof is said to be worth 5 ft.-lb. of torque at low rpm, but its length intrudes into the port resulting in a restriction that blocks exhaust gas flow and hinders rpm in the over-rev range (the part of the rpm band above peak power rpm). The 260 exhaust chest is shaped differently, with the exhaust ports being shaped more like tubes than the 280 and Drag/S3000 engines, and the slots on each side of the chest near the short side of the ports. The 280s tend to have an exhaust port height of 1.50-1.52 measured from the top of the block deck to the top of the port radius and 1.605-1.603 to the top of the port generally the same as the 260 engines. The deck height on the 280 and 260 is also about .004 inches higher than the deck on the Drag engine. The top of the entry to the transfer and boost ports is generally 4.575 inches down from the deck, which is the same as the Drag engines, but taller than the 260s at 4.751 inches measured from the deck, and gives a larger port opening than the 260 engines. The boost ports are generally set at around 2.145 inches (at the top of the radius), while the transfer ports are set at 2.110. This compares to the good 260s with boost ports at 2.135 and transfers at 2.112, and the early Drag engines with boost height at 2.110 on the outside ports and 2.065 for the center boost port, and 2.060 on the transfer ports with an exhaust port height of 1.490 at the top of the radius and 1.540 at the port roof. Realize that many of these engines will vary with their port timing (especially the hand ground Drag and OSR 260 engines) and many people measure port height differently. But basically, all of this means that the 280 engines have port heights that are several degrees lower (in relation to crankshaft rotation) than the Drag engines. And that the peak power will be delivered at a reduced rpm as a result of this. Mission: Since this is a lake engine, and lake boats tend to be heavier and carry heavier loads, building this engine the same as I would a race engine will defeat the intent of this project. First of all, a lake engine should run well on pump gas or pump gas with an octane boosting additive. Second, it should be at least as reliable as the stock engine. And third, it should produce better power over a broader range than stock. If this sounds like wanting our cake and eating it too, then follow along with the way we intend to accomplish this project. I am not a fan of the stock 280 ECU and ignition system, so for this project, 260 electronics and an A6 ECU will be used. This will allow the engine to be turned much higher for occasional drag racingshould the need present itself. Power vs- Torque: Realize that horsepower is a calculation of torque at a given rpm [HP=TQ X RPM / 5252]. So to make more power you can simply move the rpm band of the engine higher with more port timing and you have more power at a higher rpm. But you have just robbed the low end rpm of very much needed torque in order to make more power. This is the same as putting a camshaft with more duration into a truck engine, and the results are nearly the same. Personally, I think this is lazy, and usually results in a lazy engine for lake use. There are better ways to make more power in the same rpm range and even extend this range by a couple of hundred rpm on both the higher and lower ends of the power band; it just takes more work to do it. If the ports are made more efficient, they can provide flow for a couple of hundred rpm than the stock ports without losing low rpm velocity, with reasonable port timing that is better suited to the octane limits of pump gas or pump fuels with a small amount of octane booster. This efficient flow can provide a broad torque band, and the added flow allows the same torque to be produced for a couple of hundred more rpm, which will give a nice improvement to HP. A lake boat is a heavily loaded vehicle without a transmission. As a result, it needs a broad power band and lots of low end grunt to get it moving. Without the ability to shift into a higher gear, the engine needs to be able to rev well beyond its peak rpm point is you desire high speed. For this project I intend the engine to make good power over a broad range and to match all aspects of the engine details to get the most from the engine within this range while keeping most of the build up realistic and cost conscious. The only deviations will be to use some left over parts from my racing program, and these will be noted. Goals: Since we know that the 280 engines actually produce around 286 hp at 8200 rpm, we need to set a goal for what we want the engine to produce at the end of this project. Based on experience, adding 25% more power is a reasonable amount of an increase within the limits of our project, but should prove difficult to reach. This would result in 357.5 hp. Can this be achieved realistically within our limits? Stick around and lets find out! We might as well set our goals high! --------------------- Something to think about: -------------- From the above formula for horsepower, we can move the variables around a bit and figure torque. TQ = HP X 5252 / RPM. If we have a peak power of 286 hp at 8200 rpm, the above formula gives TQ = 286 X 5252 = 1502072 / 8200 = 183.1795 ft-lb of torque at 8200 rpm. [This is not peak torque; it is only the amount of torque at 8200 rpm.] If this same amount of torque is made at 8400 rpm, power is increased. TQ = 183.1795 X 8400 rpm = 15387078 / 5252 = 292.9756 hp. Realize that torque is what accelerates the boat. And that by moving the peak power to a higher rpm, a slightly lower prop pitch of higher gearing can be used to multiply this torque for better acceleration, but engine life and reliability and low speed flexibility will be reduced. A wise man once said RPM stands for Ruins Peoples Motors something to think about on a lake boat. If low speed torque is not lost (or even improved), and the additional high rpm power is there when you want it, without a loss in low rpm flexibility a win-win situation is yours for the taking. Photos to follow. Photo1 260 and 280 exhaust chest side-by-side Photo2 - 280 exhaust port roof with down-turn ------------------- END OF PART ONE ------------------------
  2. Octane Boosters

    There is a LOT of good and bad info on octane boosters available today. Basically, if you do not need additional octane for your engine to run correctly, don't add it. In most cases, running more octane than you need will slow down the combustion process, and make less power - there are exceptions to this rule. If you want to run more compression and timing advance, then you may need more octane to make more power. Race fuel is an expensive option, either running it added to pump gas, or by itself. Commercial Octane boosters usually use toluene and xylene as the major ingredients, and cost MUCH more than buying the same stuff in the paint section of your local hardware store. I am having a new STV River Rocket built that will be powered by a stock 280 Merc rotator with bolt on aftermarket parts. I am planning on changing the heads to run 185 psi compression and higher on premium pump gas with additives. This will work out some of the BS about our engines and the fuel they burn - stay tuned. below are some links that I think are informative: Toluene FAQ - http://elektro.cmhnet.org/~charlie/photos/cars/audi/toluene.html Home Brew Octane Boosters - http://www.vtr.org/maintain/gasoline-octane.html Popular Hot Rodding article 1998 - http://www.ducatimeccanica.com/gas.html Combustion controlling additives - http://www.syty.org/archives/syty/9807/msg00545.html TK-7 - http://www.bndautomotive.com/page/page/931760.htm
  3. Blank port map form

    I don't know how many of you map ports or want to. but I have included a blank port map in jpg format (like a photo) you can print off and use to map ports. I tend to print off several at a time and write all over them. I keep a binder of stock and modified port maps for reference.
  4. Hull Balance

    With all of the recent discussion on hull balance, let's start a seperate discussion on this much needed topic. My .02: The balance of the hull both front/rear and left/right seriously changes the handling charicteristics of the hull. The weight of the engine and midsection, the amount of set back, the location of the fuel tank, batteries, trim pump, etc. all affect the balance of the boat. The balance point for a light lay up hull and a standard lay up can very easily be different. The balance point front to rear will affect how well the boat launches and then lifts from the water as it gains speed. If it is too far back, the boat will launch with a bow high attitude and will be very trim sensitive at speed. Too far forward and the boat will have problems lifting from the water and can easily have problems hooking up the prop and feel "loose" at speed. Right/left balance affects the angle of the pad and if incorrect at speed will allow water pressure to roll off the pad at an angle losing lift and efficiency even to the point of dragging a sponson in the water at speed. Gearcase type can change the amount of lift and drag at the most rearward end of the lever. A stock Sportmaster tends to have a lot of tail lift that can change the way the boat handles and the balance point may need to be altered. Modifying the case for less tail lift is a better option. The location of a nose cone mounted on a gearcase can add or decrease the lift of the case at speed by changing the cone's centerline compared to the centerline of the prop shaft. A SSM has less lift, but the props tend to have quite a bit.(Others should feel free to add more on this). The tail lift of the prop can change the forces acting on the boat. Rake angle, blade design, tip cup, and trailing edge cup can all change the way the prop lifts the boat and acts on the balance of the hull. Propshaft height can change the way the boat rolls left and right due to the force of the prop and the lift of the gear case. On a right hand rotation case, too low shaft height, and the boat can have a tendancy to roll left. If it is too high it can tend to roll to the right. Way to high, and the prop can blow out at speed. Time for someone else to add their input and/or challenge this info. Dixon, Randy, Anthony, RBT......anyone?
  5. 2004 Kevlar Triad River Rocket "Special" - One of the very few Kevlar hulls, and this one was built specificaly for the owner. Only Rocket built with K1205 Kevlar instead of K900 - very strong and rigid. Hull weight - 581 Rigged weight - 1192 pounds - 1152 pounds with race fairing. Blueprinted pad Color - Boyds Hot Rod Yellow with black windscreen. Interior - White seats with yellow inserts and black piping. Carbon fiber driver's seat. Carbon fiber dash overlay Layout - 3 seat with center steering (cable). Rigging: Cable steering Full compliment of gauges - white face with yellow bezel rings Digatron DT-53 with logging. Trim Indicator - Stainless Marine In-Control foot throttle and shifter. Fuel system - Weldon with billet fuel filter. Trim - Mercruiser pump Rapid Jack jackplate Engine: 280 with Drag electronics (low hours) Custom mapped A6 ECU Brucato SVS Rubber-coated reed cages Diamond lightened flywheel with rare earth magnets Magnacor plug wires Custom modified tuner and adapter plate 15 inch midsection Drag engine cowl TorqueMaster lower unit with JC's nosecone; 1.87:1 gears Race cowl Custom fitted Sunbrella cover - yellow Trailer - Customline single axle liquid hubs torsion axels black with yellow pinstripes This is a very low hour boat that was custom built for the owner. It is in excellent condition - only used 2-3days each year. Price - USD $40,000 with choice of 2 props from large selection. For more details - e-mail Wayne Tripp at h2o_drag at yahoo.com (replace 'at' with @) more photos available.
  6. Yep, I ran into it. I tried replacing the stator, trigger, swapped coils, looked for water leaks, etc. Never did figure it out. However, I later had the injectors tested from that motor and 4 of the 6 didn't pass. Maybe something to look into. Have you removed the head(s) and looked for signs of detonation? Start by looking at the metal portion of the head gasket for dents or dings. Light detonation Also look at the pistons and heads for small pock marks. Heavy detonation The left bank (especially on the center and lowest bores) tends to ping first. If the pinging continues, detonation will set in. Detonation wis erratic combustion that causes small explosions instead of a complete burn in the combustion chamber. As a result, gas temps drop. I hope this helps.
  7. http://www.atomracing.se/index.html W-9 technical data 9 cylinder four-stroke engine in W formation with 3 cylinder rows. Cylinder volume: 2977 cm³ ( 182 in³) Bore: 90 mm Stroke: 52 mm Max rpm: 12500 Compression: 12,7:1 W-angle: 60°-0°-60° Fuel: Ethanol, E85 Head layout: 4-valve, 20° included valve angle Dimensions: LxWxH, 434x623x448mm (17,1x24,5x17,6 ") Weight: 118 kg ( 262 lbs) complete with exhaust system Max torque (est.): 380 Nm ( 280 lbs-ft)@ 7200 rpm (bmep: 15,7 bar ; 228 psi) Max power (est.): 526 hp@ 10700 rpm (bmep: 14,6 bar ; 211 psi), dimensioned for Tri-Turbo 1005 hp ENJOY! -Wayne
  8. Project 280+P (Part II)

    Execution: In this installment, we will look at what it takes to achieve our goals, and show a few photos of the differences in stock and the modified parts. Part II Compression: If we are planning to run the engine on fuel that is available on the lake, or nearby, then pump gas sets the amount of compression the engine will have and the port timing that will best suit this amount of compression and the rpm range where the majority of the power will be produced. By optimizing the chamber design and shape, the engine can be made more resistant to detonation, and more compression can be used. Adding compression is the biggest bang for your buck you can add. It increases efficiency, increases fuel mileage, and makes everything else work better. The ports suck harder on the intake flow, and the exhaust pulses work harder on scavenging and packing fuel and air back into the cylinders. Going as high with compression as you can reliably get away with on your fuel is the first place to start when increasing performance. The compression limit also sets many of the other related aspects of the engines design. The most overlooked aspect of compression is how it relates to port timing. Think of it this way, you dont run a high duration camshaft on low compression, so why would you run high duration port timing in a two-stroke on low compression. A given port timing dictates a given amount of compression. More compression than this is O.K., but less is not. As you increase port timing, you raise the top of the ports especially the exhaust port. This results in less trapped volume to compress, and more time for the cylinder to fill. To keep the efficiency the same, more compression is needed. This requires a smaller combustion chamber volume. How much smaller depends on how much port timing was added, the two are closely related. As a result of experience with these engines, it has been found that 175 psi of static compression can be run on pump gas if the engine is made as detonation resistant as possible. Many of the stock 280 engines came with 160 psi compression and run fine on premium pump fuels. So with a few improvements, we can reliably get away with more compression. And, YES, I do know this goes against common practice and internet gospel, but this is MY engine and is based on my test results. There are several factors that need to be looked into to prevent the onset of pre-ignition and erratic combustion in the chamber. The first is surface area. The amount of area the in the combustion chamber determines the amount of heat carried into the cooling system. A top hat shaped chamber gives a large amount of surface area for a given volume or chamber cc. This allows for better detonation resistance, but the lost heat is also lost power. A hemispherical or hemi chamber shape gives the smallest surface area for a given chamber volume, and has the possibility for more power, but tends to be unforgiving to detonation. The ring around the outside of a two-stroke combustion chamber is called the squish ring. This ring does two things. It pulls heat from the chamber and it gives mixture motion to the air and fuel in the chamber as the piston nears top dead center (TDC). Both of these actions are good for detonation resistance. The ring is generally spoken of as a percent of the diameter of the bore. Mercury has set many of the performance engines with a squish ring that is 50% of the bore diameter. The fact is, this works very well over a broad range, and changing this can hurt performance and mixture velocity (squish velocity). A slight angle of 2-3 degrees can give a very slight performance improvement at high rpm with a slight or unnoticed loss of idle and low rpm characteristics by changing the squish velocity slightly as a result of the angle. I generally prefer a 2.5 degree angle based on experience. The gain is small, but I like to get anything I can if little work is required. This works for the over-rev range. If you are not going to rev the engine past peak power rpm (into the over-rev range), little gain will be seen - and it is not much to begin with. The largest impact on detonation resistance that is often overlooked is the squish clearance. This is the distance between the top of the piston and the squish ring at TDC. In the chamber, there is a surface layer of heated air that is about 0.020 thick. If this boundary layer is not disturbed when the piston reaches TDC, it is very easy for areas in chamber to become hot and start erratic combustion in the form of pre-ignition or even detonation. If the piston does not get within 0.040 inches from the squish ring, the boundary layers on the piston and head will not be disturbed, and the cooling effect of the fresh fuel and air is lost. I like to get as close as I can without contact, and allowing for connecting rod stretch at high rpm. Generally, 0.037 inches is a good place to be on a lake engine that will not see long periods in the over-rev range (well above peak power rpm). The connecting rod design, weight of internal components, and maximum rpm all play a part in how close is to close, and how much squish velocity will be developed as a result. O-ring heads offer a cooling advantage over heads using gaskets by making direct contact with the block at the top of the bores where the most heat is being produced. However the metal sealing ring surrounding each cylinder on the gaskets is better for detecting the onset of detonation. If the cylinder pre-ignites, the pressure spike will leave a small ding or pock mark on the inside edge of the metal sealing ring on the gasket. I prefer to use gaskets to find the limit for compression, then to switch to o-ring heads for the added safety margin. Cooling cooler lake water means cooler temperatures inside the block. This allows for even more compression to be used effectively. Also, the 2001 and later Drag engines came with cooling tubes that direct cool water from the top center of the block to the heads between the bottom two cylinders on each bank. This is a worthwhile addition for detonation suppression. If the coolant temp on a high performance engine exceeds 125 degrees F, power will drop and the engine become less resistant to detonation. For racing, this is a big issue, and even for a lake boat it is something that cannot be ignored. The volume of water flow through the engine and the pressure of the coolant in the block need to be balanced with the maximum lake water temperature your boat will see in the heat of summer - in order to keep the engine temperatures in line. Fuel In a two-stroke engine, fuel is used to cool the cylinders. If you send your injectors out to be cleaned and flowed, you will have a list of the amount that each injector flows. You can use the effectively with a bit more knowledge. The top two cylinders get the coolest water from the top of the block, and the weakest pulse tuning from the exhaust. This means these cylinders make the least power, and need the least flow from the injectors. Put the lowest flowing two injectors in these cylinders. The bottom two cylinders get the warmest water cooling them through the block and get the strongest pulse tuning from the exhaust. As a result, they need the most flow from the injectors. These bores tend to detonate first from heat. Place the highest flowing injectors in these cylinders. The middle two cylinders get decent cooling and pulse tuning. They also get the best air flow from the intake. These cylinders tend to run in the leanest condition and can detonate from a lean condition first. If you want too run your engine with a reasonable amount of fuel for safety, the remaining injectors can be placed in these cylinders. If you want to run on the ragged edge, put the highest flowing injectors here and keep the engine fed cool water. Octane boosters On several internet forums, I have talked about the advantages of a fuel additive called TK-7. Basically in these engines, this additive keeps parts clean, improves performance about 2.5%, and at 2 ounces per 5 gallons of pump premium, makes the fuel act like it has 100 octane. This allows a well configured outboard engine to run over 185 psi of static compression and some engine as high as 195 psi. [Further testing will come in the later stages of this project.] Carbon build up - If you are going to run your engine with the most compression it can handle on the fuel you are using, you must watch for carbon build up on the tops of the pistons. This carbon build up will increase compression by taking up volume in the chamber. It also impedes airflow and can rob up to 8 hp from a good engine in extreme cases. Mercury Marine has a couple of good products for carbon removal. I also like to use a product from Gumout called Regane once a month (or every few tanks of fuel) added to the fuel. Oil Realize that some oils will reduce the octane of the fuel while others can very slightly increase it. Your oil choice also can reduce friction and heat in the engine, as well as help prevent carbon build up. I use Alisyn Pro Power oil (from Aerospace Lubricants Inc.) in all of my two-stroke engines. For lake use their biodegradable oil is clean running and very hard to beat. Their normal racing oil is the best oil I have even run. But feel free to run your oil of choice it is your engine. If pre-ignition or detonation (however mild it may be) sets in on one cylinder in your engine, the pulse tuning in the engine will be disrupted, and the tuning for that entire bank of cylinders will be off. Realize that many two-strokes run with occasional detonation most of the time. Once it sets in, it only gets worse. The engine will need to be cooled down or enrichened past the point where detonation started. Detonation will show up as a SLIGHT decrease in exhaust gas temperatures - just as if the timing was advanced a few degrees. In severe cases the pistons will fail. If you are going to push the limits of performance, there is no replacement for learning to read the burn pattern on the top of the pistons. [More on this to follow] Photo Billet heads with hemi and top hat chambers Graphic - side view of chamber with graphics and descriptions --------------------- End of Part 2 ----------------------
  9. Project 280+P (Part II)

    ttt Part III will be up soon!
  10. Is my Rocket heavy?

    Your boat looks to be heavy, but not a lot. Gas and oil weigh 6.25 pounds per gallon. Wet carpeting can weigh up to 20 additional pounds. A standard lay-up River Rocket has a hull weight of approx. 750 pounds and weighs 1325-1350 pounds fully rigged. My fully rigged Kevlar Euro weighed 1402 pounds with hydraulic steering - about 50-70 pounds less than most. Hull weight was right at 800 lbs. My Kevlar River Rocket weighs 1187 pounds fully rigged (about 40 pounds less with the race fairing installed) and had a hull weight of 576 lbs. I hope this helps.
  11. Missing Member

    Gearcase, I like the lines of the boat as well - but I am biased. The compressor is modular in design and has been developed in several sizes for engines from .5L to 9L (30-550ci). Applications are endless - cycles, outboards, automotive, aero, etc. Very light and very efficient with low drive losses (much lower than other designs). Drive systems explored so far range from belt/crankshaft, hydraulic/power steering, and exhaust/turbo.
  12. Celebrating a B-Day

    Randy, I hope you had a great one! -Wayne
  13. Missing Member

    I appologize for the absence and the delay on the 280 project...I will have MUCH more next week. It is true, I have gotten out of boat racing for the time being - too little time, and other projects have priority right now. My business is keeping me covered up, I am bringing a new supercharger to market that is right now in the late design and testing stage and moving into production. And my brother has a new boat company that I have been helping - http://www.rpmpowerboats.com/pages/1/index.htm (website soon to be completely revamped!) The 26 Redline by Revolution Performance Marine is VERY efficient, and with a single Mercury Racing 525 sterndrive package has proven to produce speeds significantly higher than any other boat design has been able to reach. This boat is the closest to an STV of any sterndrive boat that I have ever driven. The initial testing results of speeds of 100 mph developed into in us being invited to Mercury's X-Site for further testing and development that went VERY WELL. I still love my River Rocket though! And Rob, NO it is NOT for sale! I sold the DR-20 and the DRX only to get more room in the shop for other toys.
  14. Prop Science- Diameter effect?

    Diameter has a large affect on useable blade area. Reduced diameter changes the lever arm length for each blade. A 14.5 inch diameter has a blade with slightly more leverage than one with a 14 inch diameter. This gives a lower amount of slip for the slightly longer blades. Also, since a surfacing prop is only partly exposed to water at speed, and since the inner-most part of the blades are shrouded by the gearcase, the slight change in length is actually larger than it would appear. let's say you have a 14.5 inch diameter prop that you like, but cannot pull well to a given rpm. By trimming the tips of the blades a very small amount and reworking the blade tip shape, you can reduce the torque required to turn the prop at the expense of a slight increase in slip. This can get this prop an increase in acceleration by allowing the engine to get into a better area of its power band than was available before. Then by adjusting the propshaft height and/or the prop's setback on the propshaft, you can tailor the prop's bite for your usage. Example: I have a very good Yamaha 24p prop that has been trimmed very slightly. On a boat with near stock power, this prop accelerates better than it did with its full diameter. But once it gets to a given speed it hits a wall and will not go any faster. On the same boat with more power, it slips too much and still has the same top speed. I hope this helps.
  15. Fuel system

    Jeff, Since you are not using a pump to feed the vapor tank, I assume that the entire vapor tank is below the bottom of the fuel tank - otherwise, it will not fill completely using gravity. If it is not completely below the fuel tank, a check valve will allow the return from the fuel rail to fill the vapor tank if the fuel pump has enough flow. Make sure the flow of the check valve is NOT a restriction to the fuel pump. If the vapor tank is mounted level with the bottom of the fuel tank, you are not accomplishing much with the vapor tank that couldn't be done with a baffled sump in the fuel tank.
  16. Just said "I'll take it". (oop's!)

    NICE looking boat! What year is the engine? It looks like one of the 235/250 Second Effort engines.
  17. Fuel system

    Jeff, First off, Happy Easter! This has been covered here and on S&F several times in the past, but I will repeat it again since many don't understand how the fuel system works. If you are not racing, you should not be running the tank empty. You don't do it in a car, and you sure don't do it in a diesel truck or car - and neither of these sees the fuel slosh as much as a boat does. If you are RACING, then use a fuel cell with a sump. If you don't filter your fuel BEFORE it goes into the tank, any debris will get sucked into the fuel system when you run it dry. If your fuel pump is at or below the fuel level in the tank, your fuel pump is hardly working at all - think about the siphoning action. The only times it has to pull fuel is when the pick up is not submerged. A "duckfoot" or bell mouth can be added to the end of the pick up but should not be closer to the bottom of the tank than the diameter of the "duckfoot/bellmouth". Another old trick is to add a short length of flexible fuel line to the fuel pick up and to add a weight to the end of the fuel line. The FLEXIBLE fuel line will move around with the sloshing fuel in the bottom of the tank and help reduce sucking up air. If you are going to race or want to run a race fuel system like you mentioned - so you can run the fuel tank lower, DO NOT put a restriction like a check ball in front of the fuel pump! A vapor tank is really called a vapor elimination tank or surge tank. If you do suck air into the fuel system with a vapor tank, no harm is done. It simply gets returned to the fuel tank. If you are using a vapor tank, its PRIMARY mission is as a surge tank - to absorb the times when the fuel pick up is not submerged when the boat is under hard acceleration (fore/back, side-to-side), and when the fuel demand is high. The feeder pump should fill the vapor tank, this is its ONLY job. If you match the size of the vapor tank to your needs, the feeder pump does not need to flow quite as much fuel as the primary pump. The bottom of the surge tank feeds the primary fuel pump, that pressurizes the fuel, sends it to a good filter which feeds the engine. The primary pump must be matched to the fuel demands of your engine. If the pump is rated for 450 hp for a four-stroke engine, you need a LOT more capacity for a 300 hp two-stroke engine - nearly double the four-stroke flow rating - especially for a high RPM engine. The return line from the fuel rail should empty into the top of the surge tank. A low pressure check ball (like the 3 psi ones from Kinsler and others) should be mounted on top of the surge tank and used to route fuel back to the top of the tank near the pick up. This will keep the surge tank pressurized at low pressure (so the feeder pump is hardly working) and allows any air (vapor) pulled into the system to return back to the top of the fuel tank. If you do not use a check ball between the vapor tank and the fuel tank, the feeder pump needs to flow as much fuel as the primary pump. If not, the vapor tank can run dry under large fuel demands. A low pressure check ball is much cheaper than a bigger fuel pump in many cases. [Realize that fuel has weight. When you accelerate, the fuel surges toward the rear of the boat. In a car the fuel tank is generally mounted in the rear of a car and the engine is in the front. In this case the fuel pump has to overcome the added weight of the fuel under acceleration. - Just someting to think about.] Also, MAKE SURE your fuel tank has a vent big enough to allow as much air to enter the tank as the amount of fuel being pulled out of it. You would be amazed at the number of guys who don't do this and then have fuel system issues....and blame the fuel pump. A simple length of fuel line mounted to the top of the tank with 1 or 2 coils will flow well and not allow fuel to splash out since the coils act like a trap. This type of fuel system design is used in many types of racing and allows the tank to be run completely dry before the fuel system sends any air to the engine, since the vapor/surge tank and fuel lines are still full when the tank runs dry. I hope this helps.
  18. Project 280+P (Part I)

    Rob, Between business, the SC project, helping get my brother's first boat ready for the magazines, and Honey-do's, my boats are WAY down on the priority list. I have also been porting heads and throttle bodies and building a custom header for my bike (welding merge collectors and exhaust splitters - lots of fun...NOT), now that I have the ability to tune the Keihin ECU for fuel and timing. The "280+P" engine is almost finished - it is back from replating (a bit of clean up porting on the port entries is left to do), and then I need to assemble it....when I get some time. I will shoot the remaining photos, and add the next part ASAP. INCLUDING the port map of the finished engine IN DEGREES - for Galen. I normally don't give that out for outboard engines because I get stupid looks when I talk about port timing in degrees for outboard engines. ALL other two-stoke engine builders use timing in degrees (and area in square mm)....for some reason many outboard engine builders seem mystified by a timing wheel.
  19. Project 280+P (Part I)

    The rest of the photos and MORE will be up very soon. I am covered up at the moment. -Wayne
  20. octane booster

    www.bndautomotive.com is the distributor.
  21. A strange lesson learned anecdote

    Several years ago, I was buying Alisyn two-stroke oil in 55 gallon drums. I always filter and check the fuel and oil I place in all of my boats, and especially my drag boat - looking for water and debris. One day in testing, I found something that I have not wanted to mention, but it made a noticeable improvement in power. The fuel and oil were mixed in the 5 gallon race jug and checked going into the boat - nothing different. The testing session was very good, I picked up 1.5 to 2 tenths of a second over the testing that morning - even though it was now considerably warmer. When pumping out the remaining fuel at the end of the session, the fuel was milky. This meant that the fuel had water in it, not much, but enough. I mixed up another batch of fuel with a new quart of the same oil (but from a different source). The passes showed that I had now LOST 1.5-2 tenths and I was back to where I was earlier that morning. Confused, I went back to the shop. The common denomenator was the oil. So I pulled a sample from the drum - it looked normal. When I mixed it with fuel it still looked normal. When I shook it for a long time and let it sit for a few minutes, it turned milky. I used this oil in my lake boat and again noticed that it made a small but noticeable improvement in power, but that it turned slightly milky. The drum of oil had built up a small amount of condensation inside each time it was opened in the hot and humid Southern summer, and the synthetic oil had completely absorbed it. But how much water had it absorbed? I drained the drum if the last 2 gallons of oil and placed it in a large pot and put a tube on the lid. I placed the pot on a burner on low heat and ran the tube under cool water to condense the water as it evaporated. And I collected the water in another jar. It turned out that the oil had absorbed a bit more than a tablespoon of water for each quart of oil. Since then, I have run Alisyn oil in my lake boat with 1 tablespoon of oil in each quart (added to the oil not the fuel). What I have found is that it makes a small but noticeable improvement in power on higher compression levels, and even a little on a stock 280. There have been NO changes in the wear of the bores or the internal parts after several seasons. The water acts like a small amount of compression while adding detonation resistance - just like water injection. Something to think about.
  22. Project 280+P (Part II)

    Chris, The relationship between the closing of the exhaust, transfer, and boost ports helps determine where peak flow will be in the powerband and how high peak power will be made. Think of port area and duration as related to lift and duration on a camshaft. All of this shapes the torque curve - especially when you add in the effect of the volume and shape of the ports behind the sleeve. I will dig through my stuff and find some photos of a cylinder with the sleeve removed. ALL flow through the engine has to go through the rod slots, under the piston and into the transfer and boost port entries. That is why working the rod slot areas is so critical of a balance between getting enough flow, directing it where it needs to go, and not removing more material than you have to to keep the crankcase volume reasonably matched to the ports and compression used. I hope this helps.
  23. Project 280+P (Part II)

    This is a blank port map with the names of the ports for those who didn't know what the Hades I was talking about in the text above. The transfer ports are the main intake ports feeding the cylinder from under the piston, behind the sleeve, and into the cylinder. This is where the largest part of the intake charge comes from. The boost ports are additional intake ports that feed the cylinder. They generally are used to feed additional intake mixture into the cylinder after the transfer ports have closed by using the mixture velocity to overcome the pressure in the cylinder. The exhaust port lets the burned fuel and air mixture out of the cylinder. It also allows fresh intake mixture to escape during the overlap part of the engine's port timing. The exhaust pulse tuning is used to cram a good part of the fresh mixture that has escaped back into the cylinder. As a result, this port needs to work well in BOTH directions - in and out - especially the top of the port. A sharp edge on the top of the port makes good power, but is hard on the piston rings.
  24. Blank port map form

    GOOD catch Darrell (BT)! Let's try this again!
  25. Would you be interested?

    I am in the process of building a mildly ported 280 for my River Rocket. This a performance build up for use on pump gas, not a race engine. Would anyone be interested in before-and-after photos, port map, and details of what was done and why it was done? This would be a no holds barred article, all details revealed, and a few tricks shown that have been learned from racing. This is a lake engine not for racing, but with several interesting tricks. I don't want to take the time to do this if no one is interested.
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