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STV_Keith

~100mph chine walk

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Well, for the first time since I've owned my PCS, it has finally broke the triple digit speed barrier. With a custom 14.75" x 26 ET lookalike, turned my soft 2.5 to 8700 for 102mph on GPS this past weekend.

One thing I felt though, just about 97-98mph, just after it kicks the tail, the boat starts doing what I can only call chine walking. It bounces from sponson to sponson, left to right and gets progressively worse as speed increases. Trimming down makes it stick the nose and skip along, while I didn't really try trimming up at that speed.

Talked to another guy (speed alley racer) who has a 2003 RR w/drag and he says his does the same thing, but that he blasts through it (got more power than I do for sure).

We are both running sportmasters. Talked to another guy at the lake with a PCS that runs in the 105-106 range, who runs a CLE, and he's never had it happen. Is this something in the setup or inherent to the Sportmaster?

Any ways around/through it?

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Keith depending on the prop, I have felt the same thing. The odd time it seems you need to put it on the pad like a V-bottom. Some subtle mods to your sportmaster may help. I know that several STV guru's like the CLE with a cone on it over the Sportmaster.

ProComp

post-2-1098735092.jpg

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check to make sure that there is no play or movement in your steering system. I had the same problem with my hydraulic system and I bleed the system and it went away, must have been air in the lines.

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As for the "chine walk" try this first. Just yesterday I was trying a new prop (one with alot more lift than I normaly run) (A Hoss triton with 5 degrees more rake than Dave Bostic normally makes) and I had the same problem as I came up on 120mph. I was running quite a bit of negative trim so I threw 25 pounds of shot up against the front bulkhead. On the next run with the weight it was much better but I now was running the propshaft more level. Still slightly negative but not more than 1 or 2 degrees. Next we went back and raised the motor 1/4 inch to 7/8" above the pad. (propshaft centerline) Took the weight out and now it is straight and true pass 120. Granted this boat is a little sensitive but the principle is the same. With this prop I need the height but with my normal stuff it was fine before. So before you move anything, throw some weight around and see if it changes. The symptoms you described were almost exactly what I had. Same speed scrub if you trimmed down etc. One last thing, I have found that props with excessive cup will do this trait and you may want to trim some cup out the prop if your height is pretty high already. If you have little torque on the wheel now maybe you could stand to go up. If it takes a gorilla to steer it then it could be the prop itself.

Anyway, just thought I'd try to help.

Randy

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Thanks guys. I was one up, with the jackplate set at 1/2" above the pad, 6" setback. The prop is a ET clone at 14.75 x 26 cut from a 15" chopper. Very little cup in it, much like a real ET.

I noticed the same thing with my 24, just not as bad as it won't go quite as fast. The 24 is all done at 99 where the 26 went to 102 and still had a little left. I am currently limiting it at 9k.

I am getting a set of the Stainless Marine indicators for the jack plate and trim...so once I can actually see what is going on without stopping, I'll start playing with height. I can sat at 1/2" above, water pressure was no problem at all.

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Kudos, you did it! I run a Merc ET28 and have the same issue as you, especially when I back out of the throttle. Feels kinda scary, don't it? Well I think it's time you find a cleaver since you made it past 100! Cleavers handle very "nice" in the 90+ range.

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I really like the acceleration of the ET cuts. Very nice everywhere else. I'm wondering if it's something that can be driven through if I had the power to do so. Odd to me that with my 27 RE Mazco, I could only see 95mph at 7800rpm, but a 26 ET would turn to 8700 (and maybe higher if I hadn't backed out due to this instability). 1" of pitch shouldn't be that much really. I'm thinking the smaller blade area means I can turn the ET's harder.

I have also recently tried a 28 Cleaver and wasn't impressed with the acceleration and it would only turn 7600 also at 95 or so.

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Stv Kieth,

Now that you've posted a few more comparison numbers this is making sense.

Also I notice the background in your photo's, are you out west and if so what is the altitude? If the air is a little thin then that explains some things. If you like the et style of prop then find yourself some Hoss Triton 1's or the old "inline" choppers. The handling of a triton is hard to beat and I've got them to go as fast as anything on all my stv's. The inline choppers have some real top end, don't handle too bad and rpm like an et or et cut chopper. They are kind of fragile but fun none the less. I have a 14 x28 triton 1 that out drags any 26" prop I've tried. The handling comes from the 16 degrees of rake they have.(just like most cleavers) That little 28 will run within a couple of mph of any prop I've tried. Anyway, not trying to steer you but your on the bubble and looks like you just need a little more (combination or set up or prop, etc.) to really set that boat alive. I'll bet that 110 is right around the corner. I'm curious about the altitude. If you boat at 2500ft or a little more not only do you have less power but less lift. We raced F1 in Colorado many years back, at 5000ft or so. The F1 boat ran like an SST 120's up there. No power and you had to trim the crap out of them to get anywhere.

Randy

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i had the same problem the first few times i ran my quartershot. it would bounce sponson to sponson and get worse with more trim. it started around 85 and was undrivable at 110. all i did was go from 1/2" above to 3/4" above and now it drives like it's on rails.

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Randy, thanks for the pointers. I will call my dad and see what I-6 stuff he has left around from his JP and FJ racing days. I mainly boat in Havasu/Parker and Lake Mead. Mead is 1200', Havasu/Parker AZ is ~400'. Not too high.

Casey, I will try more height next time out. Thanks!

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Keith, I borrowed an inline chopper from Randy this past summer and ran 105, 2 up with it. It was apparently around a 26P. No idea on rpm as my 8K tach was buried. Accelerates pretty decent too. Definately worth a try.

I would of thought your elevation would have been higher. I think we are around 800ft here.

ProComp

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I can't say I have ever experienced the Chine Walk (sponson darting). However I have experienced something I would call (Rolling) with some high Rake RE props. It would actaully make the boat want to role to one side and lift the bow also.

Kudos on the 3 digits Keith...your on your way biggrin.gif Boat looks great

BTW...I would also run about 20 lbs in the nose of the boat (Aft of the bulk head)

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Way to go Keith and dash looks real good. Saw your helmet pic on s+f ...looks cool....so when do we get to see the full boat pics.

As for the sponson slapping, I too have experienced it with certain props. In particular my 14.5 x 30 Cleaver...in both fat stock form and recent lab form. This was while bolted to transom takes some playing to find the sweet spot. But, I don't experience it with my 15x32 lab cleaver....go figure. My 14.5x30 Tillman ET has a very short slap time but hammers thru and runs awesome....favorite prop for running on PCS.

Its a learning curve. I remember when I could'nt get my PCS w/2.4 past 80-85 without it bouncing all over....till I was told of the "STV Hump", conquered that and then face the next obstacle....we always want more. Glad to be able to resource info from BB's like these or I'd have bailed on the STV thing. SPEND, SPEND, SPEND smile.gif

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Way to go Keith and dash looks real good. Saw your helmet pic on s+f ...looks cool....so when do we get to see the full boat pics.

LOL...thanks! Pics of the boat - taken after I had it detailed: http://www.speedcraving.com/stv/stv_repair...-john/index.htm

Pics of it (and others) in the water last weekend: http://www.speedcraving.com/stv/havasu_10-23-04/index.htm

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Looks great...I like how you smoothed out the look with flush nav lites and pop-up cleats.

I still love that trailer under that boat...thanks to the previous owner before me for putting those good tires and chromies on it. He still has the original white spokes that where on it. Also I have never seen anoth STV with such a heavy duty axle and hub system. That's whatt supposedley the RACE upgrades to the trailer.

Gee I just rememberd something. Have you had a look under the tung on the tralier. My name was engraved on the bottom...you might want too grind that off. One of those things I did after it got stolen...I did it somewhere on the hull too...but cannot remember (maybe under the dash)

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Looks great...I like how you smoothed out the look with flush nav lites and pop-up cleats.

I still love that trailer under that boat...thanks to the previous owner before me for putting those good tires and chromies on it. He still has the original white spokes that where on it. Also I have never seen anoth STV with such a heavy duty axle and hub system. That's whatt supposedley the RACE upgrades to the trailer.

Gee I just rememberd something. Have you had a look under the tung on the tralier. My name was engraved on the bottom...you might want too grind that off. One of those things I did after it got stolen...I did it somewhere on the hull too...but cannot remember (maybe under the dash)

Well, a little more info here. The chine walking does seem to "go away" around 104mph. Turned a best of 107mph today at 1-1/8" up, with my 27 Mazco RE-3.

Anthony, the trailer is the next item to get some TLC. New wiring, LED lights, paint, new c-clipped-to-the-frame jack, etc. Here's a more recent pic though, with the new rims.

IPB Image

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stv keith, I have a 1990 stv procomp (total weight w/ 15 gal. of gas, offshore housing 1250 lbs.) center steer w/ a 1991 stock 260 efi, a-15 analog box, coupled to a sportmaster 1.87. Motor is mounted right to the transom, 1 5/8" above bottom to center line of propshaft. My best running wheel is a hendricks 14 x 30 older merc cleaver. At 0 degree trim boat will run 114.8 @ 8200 rpm. When I first purchased boat I called Marty at Diamond, he told me bolt motor right to the transom and set clamps in the middle set of holes. Boat drives perfectly straight, no chine walk. Also my buddy told me that boat was on top of the water and was level. Hope some of this info helps.

Edited by et07757

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stv keith, I have a 1990 stv procomp (total weight w/ 15 gal. of gas, offshore housing 1250 lbs.) center steer w/ a 1991 stock 260 efi, a-15 analog box, coupled to a sportmaster 1.87. Motor is mounted right to the transom, 1 5/8" above bottom to center line of propshaft. My best running wheel is a hendricks 14 x 30 older merc cleaver. At 0 degree trim boat will run 114.8 @ 8200 rpm. When I first purchased boat I called Marty at Diamond, he told me bolt motor right to the transom and set clamps in the middle set of holes. Boat drives perfectly straight, no chine walk. Also my buddy told me that boat was on top of the water and was level. Hope some of this info helps.

Thanks ET...I've had mine mounted to the transom before and if anything, it was slower. I like the jackplate due to the low water conditions we have around here too.

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Another update guys. Here's a picture of the trim setting it takes to get to 107mph. More positive than most say they have to run, but it ran best here.

IPB Image

And that's with a Mazco round ear RE3-27.

Well, since then, I've bought a BONE STOCK 97 2.5/260 (~100hrs, never a bolt turned, stock heads, etc), since everyone always said a stock 260 on my boat should run 110+. Well, first outings, it would turn the 27 to the 7750 limiter (A49 box). 98mph. Haven't had good enough water to try the 29, but math says it should go ~104 if I can turn that one to the limiter. What prop will it take to go 110 (if the motor will pull it) with a 7750 limiter?

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A 30cleaver should put you at 105-107 at 7700rpm. That was on the 280 limiter! When I had my euro it didn't like the RE3 27 & 29 props. Just felt like the back end was doing a wobble when running in the mid 80's and up.

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Larry,

sorry, but i disagree with you on the re3 thing. on my boat i

really like the re3, but i have a 28 on it. the drag will turn it

89-9000 on pump gas. i could go a little higher on the plate

as well. speed was 114 on gps and was still pulling. it had

a few left, just ran out of room. i think the boat handles awesome

with this prop on it, and i have left a few others drive as well

that thought the same thing.

take care,

Matt

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Matt, that Euro's got to be a fun boat with a drag on it. My Euro likes the RE's as well.

Keith if you can get your hands on a nice 14.5 x 30 Merc Clever, give it a try. The boat should run a little flatter and faster. My ProComp liked that prop.

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