Prop Pitch for your Pontoon?

[cat toon]

What prop pitch do you pontoon drivers use on your motors? I now have 15 pitch on my toon but only can get 5000 RPMs out of the motor,will get 18 to 19 miles per hour from it according to my GPS. Thinking about dropping down to 13 pitch to get my RPM up. What do you think?

 

[muskiemike12]

Re: Prop Pitch for your Pontoon?

What motor are you running and how big is your toon?

 

[rogerwa]

Re: Prop Pitch for your Pontoon?

I run a 25' pontoon with 25" toons. It has a 115hp evinrude on it. I am using a 13p hydrus prop and get appropriate wot and about 24 mph.

 

[cat toon]

Re: Prop Pitch for your Pontoon?

Sorry about that, I should have given you more info: I have 1987 70 horse Johnson on 18 foot pontoon.

 

[muskiemike12]

Re: Prop Pitch for your Pontoon?

You could even drop to a 11" pitch (theoretically) and still be under 5500rpm's so a 13" should help. Try and get a pontoon specific prop. They have a much larger surface area on the fins.

 

[lncoop]

Re: Prop Pitch for your Pontoon?

You could even drop to a 11" pitch (theoretically) and still be under 5500rpm's so a 13" should help. Try and get a pontoon specific prop. They have a much larger surface area on the fins.

Don't think so. The rule of thumb is 200 additional RPMs for every one inch drop in pitch, so going from fifteen to eleven should put him closer to 5800, which would still be fine. Looks like the recommended max is 6k.

 

[rogerwa]

Re: Prop Pitch for your Pontoon?

The hydrus I am running is a BRP (Evinrude) prop for Pontoons. Looks like it would fit your OB. It has a lot of blade surface and pretty aggressive cupped edges to maintain grip. Also, use a prop calculator to get to your slippage %. If it is high, you might solve it with cupping or motor height adjustment.

With the numbers you gave, I don't think your setup is very efficient from a slippage standpoint. Not sure of your LU ratio, but assuming it is a 2:1 ratio, your numbers give you a 46% slippage. I get about 20_25%. The theoretical top end with your specs is 35mph. At a reasonable 25% slippage you should be at 26mph.

So you need to get the rpms up and the slippage down. If you reduce slippage you may also see your WOT number reduce as well as it is getting a bigger bite and heavier load. The 11P may be the place to start.

 

[cat toon]

Re: Prop Pitch for your Pontoon?

Guys thanks for the info,my worries is that I am putting to much strain at wide open trottle only getting 5000 from the motor,I think if I could get the extra RPMs, I could trottle back from wide open and not strain my motorbit have the RPMs there if ever needed,What do you think,Am I worry about nothing?

 

[WaterDR]

Re: Prop Pitch for your Pontoon?

Keep in mind that as you change prop pitch, the amount of rpms or gain, or lose is VERY dependant on the design of the prop. For example, if you go from a 15p to a 13p AND change prop design (such as going to a bigger blade, radius, and cupping) you may actually not see an increase in rpms, but a decrease.

Anyway you look at it, you have too much prop for that motor. My suspsion is that if you had a proper pontoon prop, you will likely be able to get away with a 11p.

 

[calvinator]

Re: Prop Pitch for your Pontoon?

I just repowered my toon. I followed Mercury's prop guide. I have a 1975 Mercury 150hp and went with a Mercury 3 blade 13" pitch prop and run 5400RPM.

Pushing a 29' pontoon w/23" toons, I hit 30mph. Not really interested in top speed, but the low end torque I have is insane !

The prop guide was written in 1978 and no mention of 4 blade props. Just so happens there is a 11" pitch 4 blade prop for $100 on iboats. I'm probably going to buy it and experiment. I think I will get my RPMS, water bite, and torque up, but probably lose on the top speed.

Point being most pontoons need a 11" or 13" pitched prop.