12ft Flat Bottom Setup

[bajarick]

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.

[DeanFHobart]

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