Opinions please! Prop selection

[RaMaPhOnE]

Hi there!
I have a 17ft, 1988 Larson fiberglass bowrider.
2.5L 120hp inline 4 mercruiser alpha one drive.
15"x17P aluminum merc. 3 blade prop on it right now.
WOT is right at the top of rpm range (4600rpm)

The reason for getting a new prop is I dinged up the existing prop and need to get it fixed. The boat jumps right up on plane and does relatively well getting a 240lb person up on a tube. I'm going to keep the 17P prop for tubing/skiing.

I have found a used stainless steel 3 blade prop for a real good price.
It is 13.5"x19P.

If I have researched correctly, I have determined that it should lower my WOT RPM to 4200rpm.
Obviously it will reduce my acceleration, but my plan is to use the stainless for day to day use (fishing, cruising etc.) We only use the boat for tubing etc. for a couple weekends out of the year.
The rest of the time it has a motorguide bow mount up front with two Group 31 deep cycle batteries. Plus myself and one or two buddies.

So I'm just looking for opinions as to if this would be a wise purchase. The price is right, I just want to assure I won't be dissappointed with the performance.

BTW, he had it on a 22ft cuddy with a V6 alpha one drive.
He said it worked great for top end but the boat was too heavy and it was slow for acceleration. He figures my boat being considerably lighter, the prop should work ok.

I hope I covered everything and I appreciate and thank you for you opinions in advance.
I look forward to hearing from y'all.

Thanks,
J.
Northwestern Ontario

 

[180shabah]

Re: Opinions please! Prop selection

PASS on it.

Boat don't like to be at the bottom of the WOT range, and 4cyls hate it.

Your research probably turned up something like 1" in pitch = 200RPM. This is a a guideline not a rule. If you are comparing two props from the same line, than it is usually pretty close, but you are talking about different style props of two different materials.

WAGGY - I would bet your WOT with that SS prop would be closer to 4000 IF it could even get on plane behind a 2.5

If this is just any everday, runabout, you are better of staying with aluminum, there are some really good ones out there.
FWIW - you have nothing to gain by propping to the lower end of your WOT range.

 

[RaMaPhOnE]

Re: Opinions please! Prop selection

Thank You,
I truly appreciate your input.
I will pass on the prop...
However I must ask, should I stick with a 17P prop or go to an 18P???
Also, should I consider a 4 blade?
Thanks.

 

[180shabah]

Re: Opinions please! Prop selection

There is no reason to look at props with more pitch, there is nothing to gain by doing so. You are at the top of your WOT range, right where you want to be.

Generic suggestions:
3 blade = 17" pitch
4 blade = 16" pitch (amita stick with 17")

in general, a 4 blade will provide better slow speed maneuverability, faster planing times, lower planing speed and better cruising economy(although not enough to truly notice). They typicaly give up a little top end speed, which on a boat like yours might mean 1mph less than a comparable 3 blade.

available here at iboats for about $100:

Hustler - three blade, with vented hub - very aggressive for aluminum, favors fast hulls - don't know what you have.
Amita4 - four blade with strong hole shot and midrange pulling power

 

[steelespike]

Re: Opinions please! Prop selection

What he said^^.We have seen very good results with the Solas Amita 4 blade prop.
They seem to be very predictable with very positive results.

 

[RaMaPhOnE]

Re: Opinions please! Prop selection

Excellent. Thank you very much.
I think I will purchase the Amita 4 blade and get my 3 blade repaired when it comes in.

to answer your hull question it is a Delta Conic.