What to do?????

[colofiremedic]

I need a new prop for my pontoon boat. The boat is a 24' with an 88hp Johnson motor. The boat is used for pleasure crusing, fishing and pulling kids on skis and tubes. Since I need a new prop, I am wanting to maximize my money and buy the right prop. I used to have a 3 blade, 13 3/4" 15 P prop until it hit a rock........several times while my son was driving. The boat ran pretty well until then. Should I spend the money and buy a four blade prop or will I notice any difference. Also Stainless vs Aluminum. Any thoughts would be greatly appriciated.

 

[HighTrim]

Re: What to do?????

The best propeller size for your boat and engine combination is based on the recommended operating range at WOT for your engine.

The goal in prop selection is to determine what propeller style and size will maximize performance for your boat, while allowing your engine to operate in the recommended RPM range. The correct propeller will prevent the engine from over-revving, yet allow it to reach the minimum RPM where maximum horsepower is produced.

What was your WOT RPM? It probably should be around 5800 RPM. For every 1" of pitch size, the effect will be approximately 200 RPM. Once your wide open throttle RPM falls within the recommended range of the engine manufacturer, you have a propeller that is suited correctly for your boat with respect to RPM.

 

[colofiremedic]

Re: What to do?????

Right now my WOT is about 5200. I am thinking that I could change tha pitch a little to get more WOT RPM's. What will it do to the bottom end (hole shot if you will)

 

[Silvertip]

Re: What to do?????

If you really want to get to 5800 rpm and your current WOT is 5200 RPM you need to drop roughly 3 inches of pitch. That increase in rpm results in much better hole shot. However, I like to warn people not to spend money on a prop unless they are very certain the hull (tubes) are clean and the engine is in a proper state of tune. Installing a new prop on an engine that is not making full power is a waste and is merely putting a band-aid on the real problem. Aluminum is less expensive than stainless steel. Performance will likely be slightly better with stainless over aluminum. Three blade vs four blade is a try it and see proposition. If your son happens to hit lots of rocks, stick with aluminum unless you have a thick wallet.

 

[colofiremedic]

Re: What to do?????

ok, so here is another question....Which way do I go from 15? do I go to a 13 which would seem logical or to a 17? The whole prop thing has me somewhat baffled....sort of.

 

[colofiremedic]

Re: What to do?????

oh yea, I forgot to mention that the toons are clean and the motor runs excellent. I am not concerned with my son hitting rocks again. He thought that the boat needed to be moved soooo.....he took it upon himself to move the boat without asking. After our little discussion and the weight loss program for his 16 year old wallet I just don't see this type of thing happening again.

 

[Senderofan]

Re: What to do?????

Check your owners manual...make sure you know what your WOT rpm range is from the manufacturer. If it is indeed up to 5800....then yes, you'd get more rpm by dropping down in pitch.

I dropped from a 21 to a 19...as recommended by the guys here. I also changed from aluminum to stainless. I'm getting 200-300 more rpm at the top end. I'm also getting about 3 mph (per GPS) faster at WOT. Also, the holeshot and overall responsiveness (Bite) is a huge improvement over my old aluminum. I also think my motor sounds a bit quieter with the new prop...ie..I think it isn't lugging now...but running like it's supposed to.

I'm sure the guys (experts) can make more of a solid recommendation for you. But, yes, you have to go down in pitch to get more rpm...ie...go from 15 to 13 pitch.

Good Luck,

Wayne

 

[CharlieB]

Re: What to do?????

You mentioned changing from a 3 to a 4 blade. More blades require LESS pitch, reasoning, the additional blade surface area creates more load on the motor.