What size prop should I use? Cobra SX 1:66 ratio + 5.7l carb

[dannieboiz]

I have a 21ft Striper with a Cobra SX 1:66 Ratio, I just repowered the old 5.0l to a 5.7l. I never actually took the boat out with the old motor but according to the owner, his 14.25"x17p 3 blade prop was doing 32mph WOT and cruising 23-25mph @ 3500 rpm.

With the 5.7l i have now, i believe WOT would be 4800 rpm. I'm so used to doing at least 45mph on my old bow rider with only a 3.0l can I jump up to a 19p or even a 20p 4 blades? What about the prop size? How would that effect things? I believe the SX can take up to a 15" prop.

BTW: I'm looking for a balance of performance and speed. I would sacrifice some speed for hole shot since I'll spend some time in the deep blue seas as well.

 

[Dhadley]

Re: What size prop should I use? Cobra SX 1:66 ratio + 5.7l carb

Diameter plays a part but probably not in the way you might think it does. Right now we need to establish your baseline with the existing prop.

Have you run the prop you have and if so what were the top rpm and speed? Will it turn up only 4800 or will it go more? What brand and style prop is it?