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STVorHST?
05-21-2001, 05:32 PM
I am new to the STV's and would like help on best setback on a 94 STV / 2.5 EFI. Currently mounted directly to transon. Any suggestions would be appreciated.

Thanks
Mark
STVorHST?

hotrodtodd
05-21-2001, 07:55 PM
mark what kind of stv do you have ?Is your 2.5 a 260 or a 280?

STVorHST?
05-21-2001, 08:02 PM
It is a Pro Comp with a 260, However the original literature from the previous owner shows it as a Comp/Racer?. We just weigh'd the unit tonight without motor and fuel and came up with 733#'s This doesn't match anything that I've read. Who knows...

Firestarter
05-22-2001, 07:50 AM
That weight is about right. The pro comp runs best with the motor in the middle bolt hole on the transom.
14.5 X 32 cleaver will be quickest, and a 28 ET for good acceleration.

RT

AnthonySS
05-22-2001, 09:24 AM
RT is RIGHT!

The advertised weight on a ProCompSki was 825 lb. Add doble kevlar and the weight can be as low as 775lbs on a full interior boat.

RT has done alot of testing on these boats and yes they run best stuck on the transom. Roarke Summerford said the same. You loose about 3 mph with a setback, however the setback could have some other benefits.

I use a 5.5" CMC mostly for added clearance when tilting the motor and for more leverage when loaded.

Sincerely,

AnthonySS

Raceman
05-22-2001, 09:31 PM
Both my STV's have mod VP decks with one of each style bottom. Both were rigged with 20" motors (slightly tweaked 260's) when I bought them. Ruark told me on the phone to run them with the motors on the transom with no setback. I changed both to 15" Merc SS housings which required either 5" of setback or butchering the boats. I chose the setbacks. Also the 15" Merc swivel bracket has an extra 2" of setback, so I went back 7" total. I don't think the setback helped or hurt the speed, but it did cause the mid range porpoise which was barely present with the motor on the transom to be much worse. I'd run it flat on the transom if I had the choice. I run 32 cleavers on both mine, one with a sportmaster, the other with an XR6 (1.78 gears). I think the boats run/handle much better with the cleavers than the round ears.

RocketMan
05-23-2001, 10:30 AM
I had a 1989 STV from 1990 to 1995. I drag and river raced the boat with a variety of 20" 2.4 EFI's and 2.5 EFI 260 Mercs. I bought the boat used, so I don't know what the official factory model name was, but I can describe the boat. It did not have the circle race (Mod VP) deck. It had the wider cockpit pleasure boat deck. It had a Kevlar bottom and no interior or floor. Bare hull weight was 560 lbs. One lighweight race seat on the centerline and a race rear fairing. The previous owner said it was called a "Drag Special".

It was built just prior to the switch to the inverted "V" pad design. I don't know what purpose you have in mind for yours (race or pleasure) and I don't know how much interior your boat has but I can tell you how I set mine up:

1) I ran a Mod-VP gearcase with Bob's nose cone approx. 5/8 above the pad.

2) Bottom was blueprinted and painted with Dupont grey primer. Wet sanded parallel to centerline with "Ultra-Fine"
paper.

3) I ran a very light home made 4 and 3/8" set back.

4) Generally ran a 14.25 x 27 SSTRX worked by DAH.

5) The boat was brutally quick in it's day! Capable of 10.00 ET's old USDBA starts.

6) Handled perfect whether riding the river or drag racing! No bad habits at all in a straight line! It did have a tendency to hook hard if you pushed it too hot into a turn. This was due to the set-back and engine height.

7) My STV experience predates GPS speed readings, but with a 14 x 28 Hoss Triton, and the 2.5 EFI with heads and reed plate spacer, it would do serious damage to a Medallion 125 MPH speedo needle! 14 x 28 Merc Cleaver was a fast and great handling prop as well. I agree with above that the cleavers handled real sweet, but, I always felt the SSTRX was the quickest in a rolling start drag race. The guy who bought the boat from me ran a yamacopy prop that worked real good in an in-gear idle drag race situation.

8) I never ran the rear fairing. Didn't help top end enough to justify 11 lbs. of extra weight.

Of all the hot rod boats I've owned, this one was the best handling, fastest mph, easiest to drive and the one I would like to have back some day!

Have fun, be carefull

Paul

fasteddie
05-24-2001, 06:02 PM
I have owned numerous STV's and have been involved with testing on many also.
Bottom designs are a tossup regarding the Mod vp and the ski bottom.(don't notice alot of difference).
The old v sprint bottom we have found seems to accelerate harder but won't quite run the top end numbers and like motor ran a little lower 2nd hole from top
Set back' we have found only helps on take off and does make a porpoise at cruising speed.
mod and ski bottoms run bolted direct in middle bolt hole.
Have run CLE gearcases without problems but do prefer nosecone.
Very Very partial to Modified choppers or ET, for all around lake use, in around a 24 to 26 pitch depending on power.
like yami's for drag props 22" to 24"
We like to make them accelerate here and don't mind turning a few more rpm.
ed

hotrodtodd
05-25-2001, 10:26 PM
I have a 90 ski comp seats 4, with a 98 2.5ss with 10"of set back.I haven't had the boat that long, still tring different setup's.I tried running a 14 1/4x28 alabama cut,a 14 1/2x26 yamaha copy,and a 14 1/2x31 hoss,but the motor was getting on the rev limiter at 7750.Just got a chip with no limiter,also adding a svs intake. The motor is 1/4" above the pad may go up another 1/4".I'll try it like it is first this weekend.