1990 Johnson 90 hp rpms

[coin operated]

I just got this motor. It seems to run great. Starts first try, idles smoothly, shifts smoothly with no hesitation, takes off great and runs good. It will push my 1973 trihull about 35 by the speedo (gps is down, so i don't have gps speed). I just installed a Faria tachometer. It also seems to be working well, as it shows it idling at about 800 in the water, and it climbs as I increase speed. BUT at full throttle I am only showing 3000-3200 rpm at about 35 mph. Reading on line shows that WOT should be 4500-5500 rpms. Any ideas? Thanks for your help.

 

[jakedaawg]

Make sure the hull is not waterlogged, if it hasn't been restored then it most likely is. After that it's prop time. What is the current pitch and diameter?

 

[Chinewalker]

And make sure the tach is set correctly to whatever position is recommended for your motor.

When all is said and done, prop it to reach the upper end of the RPM range, if not a little more. I have a 1984 Johnson 90 that peaks around 5800 RPM at full tilt boogie and a light load.

 

[Lightwin 3]

And make sure the tach is set correctly to whatever position is recommended for your motor.

When all is said and done, prop it to reach the upper end of the RPM range, if not a little more. I have a 1984 Johnson 90 that peaks around 5800 RPM at full tilt boogie and a light load.

I agree. Don't always trust the tach.