1989 Classic 40 2stroke won't surpass 4000 rpm

[DTN]

I recently bought a 13ft whaler with a merc 40 classic from 1989. At full throttle the boat will only do 15mph and wont do over 4000 rpm. I've change the spark plugs, done a compression test (120psi on all cylinders) and changed the fuel line. It doesn't sound funny, no sudden change in sound. The prop is stock too, I'm stumped.

 

[racerone]

Check for spark on all 4 leads.----Spark must jump a gap of 3/8" or more.--Remove lower unit for new impeller --Check exhaust tuner for blockage.

 

[DTN]

It just got a new impeller, but yes I will check for spark. You said exhaust tuner where is that exactly?

 

[racerone]

With lower unit off use a strong flashlight and look up into where the exhaust comes from.

 

[Silvertip]

Throttle cable properly adjusted? Throttle plates in carburetors opening fully? Timing advance link properly adjusted and not disconnected. Do the easy stuff first. All of these items are simply "look at it" troubleshooting and its free..

 

[DTN]

I found out that my "throttle actuator" is broken, trouble is that it's discontinued. Going to attempt to fix it and cross my fingers.

 

[DTN]

I've also discovered that the battery isn't getting charged. That could be part of the problem