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STV Mod VP Engine Height

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1996 STV Mod VP (the hull weighs 605lbs without rigging)

260 drag making about 350hp

15" mid

stock 200 2:1 gears with lower with bob's conversion

4" Manual jack plate

24 and 26 pitch yamaha prop

How much above the pad would give me optimum 1/4 mile performance?

It is currently 1/4" up and I have found such a wide suggestion of height from 1/2" to 1 1/2" up but most threads seem to be people running the motor straight on the transom.

At 1/4" I turn the 24 10k before it runs out of pull at around 100mph +- 4mph.

So, would the suggestions be to leave it where it is or go up? It was set about even and it got really scary on the top end wanting to dart left and right, where it is now it handles good but I am thinking it may be tough to get an 11 second 1/4 mile time which is ultimate goal.

Any help would be appreciated.

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What's the Dia on the Yamaha? are they 14 or 14 1/4"?

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I would go 1 inch above the pad which always worked best on my Euroski with various props. I even tried an old 13.75 x 28 Hoss Triton which was 2mph faster then my 28ET.

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I would go 1 inch above the pad which always worked best on my Euroski with various props. I even tried an old 13.75 x 28 Hoss Triton which was 2mph faster then my 28ET.

14 1/4 diameter.

I am thinking 1 inch as well. Also considering going with the 26P yammie of same diameter since I am running the 2:1 gears. Should help a little with the top end of the 1/4 mile. As it goes I am already turning it 10k at about 3/4 track with the height set at only 1/4 up from center. My fear is that if I did raise it and run the 24P I would probably rev to 10500 and I wanted to keep it 10k or less since 10k is hard on a motor.

Thanks for the responses. Any other suggestions of course would be welcome.

post-6120-1243903326.jpg

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Most will say keep going up in 1/8" increments...I usually went up by 1/4". When you start to feel the boat starting to come around on you is when you are too high (paddle wheel the stern around). Larry's suggestion sounds good but at 14 1/4" dia you won't be able to carry the hieght of 14.5 or 15 wheel. which may be ok for drags anyway...nice boat and performance sounds nice...play safe

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The 26 pitch is my friends and it is a 14.5" so with that knowledge combined with the 2:1 gears I think I may just buy it from him. He is wanting a lightning ET. Maybe I will try to find a good deal on the other prop and take this one off his hands. would be a nice prop for the collection and sounds like the slightly larger diameter would be good to have it. My lake prop is a 28 round ear 14.5 but thinking of selling it since I am not a big top end guy anyway. It seems to run ok on the boat though I know if I raised the motor it would really wake up the mid and top end on this.

I appreciate the feedback guys. I think I will go up 1/2" which would bring me to 3/4" up and be a better starting point that only 1/4" up as it is now. When I first got the boat it was about 1/2" below and while it would rip your head off on the launch it had the typical sponson darting issue which for that to happen at about 95-100 mph it scares the hell out of you.

I will let you guys know the result. Probably will be seeral weeks before I get the chance to test it out but I will let you guys know how things turn out after Augusta and High Point races.

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X-cellent...keep us posted

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Just got back from the lake. I tried a new yama 26 without moving the motor at all and was able to wind it up to 10,100 with the 2:1 gears so I am thinking it may be a little fast for the 11 second class. Ran the math on the prop slip calc with 9% slip and actual speed came out to 109. Thinking I may need to acrub about 10 mph to keep from breaking out. Will find out more next weekend in Augusta on the clocks. The 24p may be the way to go though since it launches harder but tops out in the high 90's low 100's as it has not been reworked and is actualy a bit slower. I will post more after the races.

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Well ran the boat in Augusta this weekend left the engine at 1/4 inch up from the pad and ran a best time of 10.4 seconds in the 1/4 mile at 107 mph and the boat handled great. I used my 24p yammie cut to put up those numbers. Boat ran really consistent 10.6's at 99mph. Wondering now if raising it a 1/2 inch or so would allow the boat to run 10 flats. Going to run it again this weekend in the High Point drags and will post once I find out.

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sounds like it is all workin good...:)

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I run a STV pro comp 96 with 98 mariner 260 that is running 182 lbs compression bobs 6 inch set back hyd. lift. best run 103 1/4 mi. with modified yamaha 28 pitch 14 1/2 dia. 8200 rpm. best top 116 on gps masco 28 pitch 7800 rpm. They both come out so hard that it is easy to water ski with. If you are pulling that high of rpm your slip ratio is to high

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Do any of you sell or know someone that sells its STV? has to be a 91' - actual

for Enduro racing 2.4L - 2.5

best regards,

Jorge

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Hello, I am new to this site and also a nex STV owner. I have been working on the wiring and engine. I noticed that the previous posts talks about a Yamaha prop. I am wondering if this is the best prop to run on my 1986 Pro Comp? It appears somewhere in the 24 - 26 pich range and 14 - 14 1/4" diameter? I have a 2.4 bridgeport EFI that I will be running. Any help would be appreciated.

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If it's a 240hp BP and your're not drag racing then I would think a 28p like an ET type prop, or 30p for a cleaver.

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