I had 17 ft with 5.7 vortec repower 300hp upper unit 1.5 rator would some one help me choice prop propeller 3 blade or 4 blade and 5 blade with one right for my boats ,,,I used my boat as ski and pull tube ..

what prop do you have now, blades, diameter, pitch?

How many RPM's do you get wide open?

What is the GPS speed wide open?

my boat is v6 4.3 but engine was take out to modified v8 and upgrade upper unit to 1.5 the boat not on water to test drive yet I juist plant for propeller ,but most progress about done

You really need to find out the information PSTORTI asked. I would start with a 3 blade stainless with 19" of pitch. That will put you in the ballpark for starters. A 4 or 5 blade in the 18" pitch range would also get your started.

Nope, go bigger. That will turn a 23 I bet. Mine does and it's 2 feet longer.

i knew of a guy to retrofitted a 350 mercruiser in a searay 160 he ran a solas 4 blade 19p and ran at 65 scary speeds for small boat but definitly cool idk much about the solas props other than we used to use them in seadoos but they are pretty bang for the buck

ok, that is a small boat with a lot of motor. you changed drive ratio from 1.65 or 68 to 1.5. there is 2 inches of additional pitch (effectively) right there. you didn't even say what pitch or dia your prop is. but the first thing you do is run what is paid for and see what speed-rpm you are getting. but don't let it go over 5500 just to see how high it'll rev. also, remember no matter what you run, that boat will be going dangerously fast before you hit your optimum speed/rpm sweet spot. you DON'T wanna be much over 60 mph with that set-up...

THANK YOU dereknkathy,i will do safety way,it just build for fun,i am not put my life on it thank agian