Johnson 115 prop help

[Mopardan]

We have a 99 model Larson 186 SEI F/S with a 99 model Johnson 115. It runs about 40 mph with 3 people @ 5000 rpm. Not sure what max rpm is, but I think is 5500. It has a aluminum 14x17 prop. Problem is as the kids get bigger (growing up) it getting harder to pull them up on ski's. Losing a few mph not a big issue. Thinking of going to a lower pitch prop, but not sure what would be best without trial and error. 3 blade, 4 blade? Anything else that might help? Boat rated for 150hp, but a new motor is pretty much out of the question.

 

[hwsiii]

Re: Johnson 115 prop help

Dan, if you will change your prop to a 15" Pitch in the same model you have now you will gain about 500 RPM up to about your max recommended RPM with 3 people on board. You will also find that your hole shot and pulling power will increase a lot, it will make pulling the kids up much easier, but you may have to watch out for over revving the engine with only one person on board. You will be very happy with the results and it will cure your problem.

H

 

[Mopardan]

Re: Johnson 115 prop help

Thanks for the info. Went to the lake Mon and Tue and it ran 38 mph (by the spedo) with 2 people, and trimming almost to the top of the guage I got 5100 rpm. Any higher and it sounded like it was trying to vent. Would I lose much top end with a 15 pitch @ 5500? Thanks.

 

[hwsiii]

Re: Johnson 115 prop help

Only 1 to 2 MPH, and if you are carrying a light load you wouldn't want to trim it way up because the RPM may go to 5,600 RPM.

H