'99 Johnson 115 Prop - RPMs too Low?

[Captain Jeff]

Hello,

1999 Johnson 115 J115PXEE on a 18' center console. I have a 14 1/2 X 19 prop on there now and I can get around 37-38 MPH at a WOT of 5,000-5,200 RPMs. Maybe I can get another 50 RPMs if I tweak the trim. From what I have read, I should be running at a higher RPM at WOT. I am looking at getting a new prop. My questions are:

Should I get a different size diameter or pitch prop?

How many splines does my prop shaft have?

Thank you

 

[wilde1j]

Re: '99 Johnson 115 Prop - RPMs too Low?

Target should be 5800 RPM @ WOT. If setup is right, you need a lower pitch prop. A 17" pitch will gain ~ 300 to 400 RPM. Is engine high enough? If it is, AV plate will be running dry @ WOT. If it's buried, raising motor will increase RPM, speed and fuel economy. Keep raising until the AV plate is dry and motor doesn't cavitate excessively in tight turns.

Diamter of prop has almost no effect. Count the splines ... I have no idea how many.

 

[ezeke]

Re: '99 Johnson 115 Prop - RPMs too Low?

X models have the large gearcase with the 15 spline propshaft.