Need more prop?

[MaxOD]

I have a 3.0 Volvo Penta SX on a 17.5ft Regal bowrider. Just had the engine done and went on the first trip today. It planes pretty good, not as quick as my 16ft Starcraft aluminum, but this is the first stern drive I have had. I got 38mph on the speedo but it was screaming. The tach is brand new but reads very unstable at high speed. Give or take about 1500rpm. Another problem. My best guess is about 5500rpm at that speed and thats as high as I let it go. It was still climbing. The prop has the numbers 15X17 stamped on the hub. Is that dia and pitch? What would you suggest for a better size prop to bring the rpm's down to a more reasonable 4500. Like I mentioned, I haven't owned this type of boat before or even rode in one so I don't have a clue what the hole shot should be like or how quick it is to plane. The engine has been blueprinted, with 327 pistons cut to 0 deck height so its a bit stronger than stock but I don't want it turning so fast and I don't want to lose all the bottom end. Thanks

 

[rndn]

Re: Need more prop?

It looks like you would need a 21 or 22 inch prop. You can plan to gain or lose 200 rpm's for every inch of pitch change. Realize that this is a close estimate and only when comparing props of the same design from the same manufacturer.

 

[MaxOD]

Re: Need more prop?

Thanks, I will try a 21 pitch and see what happens. If I can cruise at a comfortable rpm I can always change it back for pulling tubes.

 

[xxxflhrci]

Re: Need more prop?

5500 is way too high.

I have the same size boat and engine. I run a 19. It turns 4600 at WOT and tops out at 40. The boat gets up on plane quickly and has no problem pulling the two grown men on tubes or kneeboards.

 

[MaxOD]

Re: Need more prop?

5500 is way too high.

I have the same size boat and engine. I run a 19. It turns 4600 at WOT and tops out at 40. The boat gets up on plane quickly and has no problem pulling the two grown men on tubes or kneeboards.

That would be all I want to do. I was at the local boat supply store today talking props and they are good enough to let me try a 19 and a 21 as long as I buy the one I want and don't damage them. It seems the higher in pitch you go the smaller in dia. they get. The guy told me that the smaller dia. will help your hole shot out with out sacrificing too much off the top end. Be interesting to see.