1999 Johnson P90PLEEB Surging / RPM Fluctuating

[EMKFLYER]

Hello, I just got a 1999 Key West with a 1999 Johnson P90PLEEB. It starts, idles, and runs as good as new. However, it seems like when I am running around 3000-4500 RPM I'm getting about a 300 RPM surge that is noticeable on the Tach Gauge and by the seat of the pants.

In the last couple weeks the following has been serviced: New spark plugs, compression checks good, timing is good, rebuilt carbs, replaced lower unit due to broken skeg, replaced spun hub and prop shaft, changed fuel filter, changed impeller, and replaced the thermostat.

Does anyone have any ideas? The boat and motor run great. It's just this 300 RPM fluctuation is driving me crazy!

Thank you for any help,
Ed

 

[Daviet]

Re: 1999 Johnson P90PLEEB Surging / RPM Fluctuating

Try pumping the primer bulb while it is acting up, maybe you have a fuel pump going out.
You can use an inductive timing light to check eack plug wire to look for irratic spark on a cylinder while it is under load, maybe you have an ignition component breaking down under a load.