slightly heavy pontoon boat would like to reach proper rpm.

[Standupguygt]

On my pontoon I have a Johnson 40 hp from 1993. It doesn't reach the peak rpm of between 4500-5200. Cursing by my self its at about 4,300 rpm and gets worse with each extra person that steps abord. I bought the lowest pitch Johnson makes for this motor. I even tried a Solis which was pitched lower but it has a problem with cavitation. It had a conversion kit with which adapted it to the exhaust and shaft but it just doesn't work. My biggest question is, in theory I could grind a little off the each blade to get less surface area to basically get rpms up. anyone ever do that?

 

[Standupguygt]

On my pontoon I have a Johnson 40 hp from 1993. It doesn't reach the peak rpm of between 4500-5200. Cursing by myself it's at about 4,300 rpm and gets worse with each extra person that steps abord. I bought the lowest pitch Johnson makes for this motor. I even tried a Solis which was pitched lower, but it has a problem with cavitation. It had a conversion kit with which adapted it to the exhaust and shaft, but it just doesn't work. My biggest question is, in theory I could grind a little off each blade to get less surface area to basically get rpms up. anyone ever do that?

Also, I noticed a slight cupping on the prop. Could that account for a little bit of my problem?
I'm sorry for not having the pitch and prop model type. I'm in northern Michigan and everything is wrapped up for the season.

 

[Scott Danforth]

In the UP? Or just northern MI?

Reach out to Green Bay Propeller and have them de-cup your prop

 

[airshot]

Cupping helps the prop to bite into the water but it adds to the " pitch" of the prop as well. Before going thru a bunch of props, go thru your motor to be sure it is running at its peak. Many times people spend big bucks on props only to fing their engine is worn out or has other issues!! In my 60 years of boating have never saw a case of a prop not availiable in a low enough pitch, thus my concern for your motor not performing at its best....let us know what you find..