12ft Flat Bottom Setup

I have a 1236 flat bottom with a 25hp Mercury turning a 15 pitch Powertech SRA3. I originally had the jackplate set as shown in the third picture. I was turning 6000 rpm and hit 39mph. I raised the jackplate one set of holes to the height shown in the first and pictures. I was turning 6300 rpm but still only running 39mph. The trim pin was in the fifth hole both times, which is just barely positive.

Would it help to add some cup to the prop? Or do I need to drop the jackplate back down and be satisfied with 39?

I'll let someone with way more experience then me give advice, but I just wanted to say it is awesome to see people doing this with the flatties still. I sure miss playing with mine.

Good luck to with setup. I hope you bust 45mph one day haha.

This was my little 14' setup with a merc 50.

You might try a full lenght cavitation plate to keep more water around the prop to prevent blow out at the upper height if you want to stay with the Power tech prop. Not saying it will go faster, but rpm increase with no mph increase suggest the prop is losing grip.

Plan B, and my faverite is to call up a custom prop shop/guy like Ron Hill and let him put you on what you need.

Looks fun.

Rob



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I would try increasing the pitch of the prop an inch or so. Your RPMs went up cause you raised the engine - but your speed did not pick up much because the pitch was the same. Your probably as high as you can go without losing cooling water pressure with the stock water intake location.

I would say that 39 mph with a 25hp is really good. Yes, get Ron Hill to help you.