Omc 25h.p.

[Skoontz]

I would strongly suggest using modeling clay on the top of the piston then run it to TDC. Mic the clay to see how much room you have. Typically, .060 was what we used to take off. We took .100 off once and ended up having to gouge out the corners of the cylinder head to match the pistons.

We ran "blue" Sunoco 260, then it turned red but still gave you a headache if you spilled it on the concrete floor. Take AS MUCH as you can then pick up some octane additive from the suto parts store....

[DonChichoJr.]

Thanks For The Reply.
What Brand Of Octane Booster ??

Don

[Skoontz]

STP had one at one point that worked fairly well. The other thing you could do is get 5 gallon cans of VP racing fuel, ($ 8.00 a gallon)or yet another trick is head to a local airport, one that has small planes and buy aviation fuel, $6.00 a gallon).

Either one worked well but I'm personally a VP guy..

[DonChichoJr.]

I Would Like To Shaved .030" , And Using 50/50 , 95 Octane Gas/ Av Gas . .030" It's Enough To Feel The Difference ???

Don

[Skoontz]

I've said this before. The biggest jump you will see is what you can do to improve hydrodynamics first, i.e., below the waterline. Gearcase, bottom of the boat etc. If you shave a head and that's all you do, you'll get a little more bottom end and that will hardly be noticable. You add the head work to anythign else necessary to getting more RPM, then it will work in sync with all the other things you have done.

As far as taking .030 from a stock 25HP head, it should be no problem at all, but as I mentioned before, check yourself the cheap way by using modeling clay, then measure how thick the clay is.

[DonChichoJr.]

Thanks A Lot !!!!!!!!!!!!!

Don

[JohnsonM50]

Heres the almost done 102-OMC lower, the 102 half remains origional but will work on a 25hp johnrude [or 35] and have a water pump.

[RichardKCMo]

Not enough words, so gets reg. to 93 octane i think, but google knows for sure. Oh Skoontz is right that's the first most important place to start.

Thanks For The Reply.
What Brand Of Octane Booster ??

Don

[JohnsonM50]

Heres the almost done 102-OMC lower, the 102 half remains origional but will work on a 25hp johnrude [or 35] and have a water pump.

I finally got it in the water at a teeker meet, it shows alot of promise. After only a barrel test to go on I put it on a C hydro 2in. deep to be sure of cooling. It went about 57, when I bring it to height I think itll move out.

[JohnsonM50]

Thanks David, Cone? Yup and nah, the foot will still bolt up to my I02, want to keep it stock. I ran both the OMC and the 102 Saturday on the same boat. The OMC has a 6.9 ci. advantage and is stripped of hardware and cowling so weighs near the same. I had the 102 3/4in deep and it went faster but theyre close. The real difference was in how smooth and effortless the 102 seemed compared to a screamin shakin fishin motor leavin a trail of bolts behind. Ill have to get a balanced powerhead on that.