Lugging engine - 70hp Evinrude on pontoon

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Have a 70 hp Evinrude with a 13 3/4" x 13 pitch prop (alum). It is on a 20 ft. fiberglass pontoon boat. Max rpm is 5100 with 2 people on board. With 5 or 6 on board it really lugs the engine and I get about 4600 rpm max. Thinking of going to a 14 x 11 prop (alum). Am I correct to go this way? Thanks

 

[steelespike]

Re: Lugging engine - 70hp Evinrude on pontoon

The 11 would increase rpm by about 400.I wouldn't look for much speed change but I think the motor would be a little happier.

 

[Dhadley]

Re: Lugging engine - 70hp Evinrude on pontoon

There are props made specifically for pontoon motors. You might consider one of those.

 

[finish line 88]

Re: Lugging engine - 70hp Evinrude on pontoon

There are props made specifically for pontoon motors. You might consider one of those.

I purchased the prop from the local marine dealer and they gave me the
13 3/4 x 13 for the pontoon. I am not interested in speed as much as not lugging the engine. Any direction as to sizes would help or where to look. Thanks

 

[Dhadley]

Re: Lugging engine - 70hp Evinrude on pontoon

What brand is it? 3 blade or 4? Is it made specifically for a pontoon?

 

[finish line 88]

Re: Lugging engine - 70hp Evinrude on pontoon

It was a OMC prop with 3 blades. It did not say anything on the box about being for a pontoon. Is it the cup of the prop that is different? Thanks

 

[Dhadley]

Re: Lugging engine - 70hp Evinrude on pontoon

Yes, that's a prop made for pontoons. See what a good choice you made?