OK guys, I have a 383 mercury engine coupled to a bravo drive. The engine puts out about 350 hp in the drive ratio is 1:50. The boat is 19.5 foot. Any ideas on the pitch and propeller diameter I should use? Should I call mercury racing and ask?

I had a 19' Checkmate with a decent 400sbc. It made an estimated 350plus hp. The best prop we found was a 27" Mirage plus from Merc. We could turn that just over 5K and had great bow lift.

What engine was in it before ? What prop ? How did it do - planing, top speed at what rpm ?

I'd start with a 23" Mirage Plus, and go up from there. You SHOULD be able to pull 4800 - 5000 rpm, and if so, go up to a 4 blade Rev 4 in 24", see what happens. DOUBTFUL you'd be able to do a 25" Mirage Plus but worth trying for top end, but the hole shot would probably suck beyond belief.

https://www.mercurymarine.com/en/us/...lers/selector/

You might give Rich Junker over at leading edge propellers a call he's very good at propping boats.

In boat that small the tempest plus might also work well. In my 22ft hull with 380hp 383cid, mirage was the worst ever prop, and tempest worked perfect.

I was thinking the same thing. So far the fastest prop on my 22' Baja has been a worked over Tempest.

With a small block and a 20 ish foot boat starting out in a 19-21” 3 blade will be the best starting point. Laser II or there about.