i need some answers about new prop i bought today

[captlucky13]

i was running a 19 pitch prop kind of chewed up. i had a 305 chevy. i just had a 350 chevy put in brand new ran this boat but it was underproped i was hitting only 40 at 5300 rpm. i now have a 14 1/4 21 pitch prop votex i just got today and installed it. can anyone tell me what this will either do to my top end speed or rpms this is important. i am eventually getting a 4 barrell and hope to make a push for 50 55 mph can someone help thanks

[Curmudgeon]

To answer your question(s), one would need to know what is red line RPM for your motor, and what prop did you previously use. Educated quesses can then be fabricated ...

[mikebcfd]

Lowering your pitch will raise RPM's but drop your topend speed. Highering your pitch will drop your RPM's but raise your top end speed. But you need to find out what the operating range is for your RPM's for your engine.

Pitch = how many inches your prop will travel in one revolution.
Lowering or adding Pitch usally ads or takes away 200-400 RPM

[ken2]

The 21 should hold your rpm down about 300-400 rpm. Depends on if you switched brands of props or went with the same style and just a higher pitch. If you switched brands, then its a toss up on what will happen.
Most likely you'll run 3 or 4 mph faster at about 4900 rpm.

you need to find the rpm range of the new motor, and prop it to get near the top end of that range.

Higher pitch in your case, should give you faster top end, but thats not a blanket statement.
When you go too high in pitch and over prop your boat you will loose speed as well.
If higher pitch always equaled higher speed, I'd sell a lot of 36 pitch props.