Looking for prop advice

[Seapro255]

Boat is a Sea Pro 255 walkaround with 5.7 Mercruiser/Alpha 1. Approx weight loaded is about 6000 lbs.
The prop that came with the boat is a Vengeance SS 14-1/2 X 17P. WOT is 41 MPH (GPS) @ 4200 RPM

I tried a Vengeance 14-1/2 X 15P and got 38 MPH @ 4900+ RPM when trimmed out it will actually cause the
rev limiter to kick in.

I was thinking about buying a Mercury Black Max alum prop to try 16"dia X 16P any thoughts on this?

 

[steelespike]

Re: Looking for prop advice

Welcome,
We need the gear ratio(usually on the leg) and/or the year and horse power.

 

[Seapro255]

Re: Looking for prop advice

1999 Alpha 1 Gen II pretty sure its 1.47

 

[steelespike]

Re: Looking for prop advice

Are you just trying to nail the rpm?
I believe the rpm rating is 4400-4800. I think I would see if a prop shop could add a little cup or an inch of pitch to the Vengence 15.
I don't think an al prop will measure up to the vengeance.

 

[Seapro255]

Re: Looking for prop advice

I would like to get the RPM's within 4400-4800 and hope for the best performance. The 17P prop seems to have more cupping than the 15P. I guess that may explain the 800RPM differance. I don't know if repitching would be the most economical option, that is why I was thinking of trying the Alum 16P with the larger diameter.

 

[angleness]

Re: Looking for prop advice

Welcome,
We need the gear ratio(usually on the leg) and/or the year and horse power.

hi ,i am new here .nice to see you here .

 

[steelespike]

Re: Looking for prop advice

The 16 seems like a reasonable approach but when going from ss to al results become unpredictable.
A 16" at 4700 10% slip indicates about 43.Thats assuming 10% like your 17" ss prop did.