1999 Johnson 90 Hp PLEEB Lagging, surging

[83mulligan]

Hi all. I have a new to me Johnson 90 Hp. Took it out and ran it over the weekend for the first time. Does great until about 2500 RPM. Then, when I give it throttle it will lag, then surge, run a bit, then lag again and surge. Has a lot of trouble running between 4000 rpm and WOT, which appears to be 5000 rpm. On one little trip, it ran fine, even to WOT with no lagging and surging. Next day it was back to acting up. Is this carb buildup? I put a can of seafoam in 18 gallons, but as of yet, that hasn't done much to help the issue.

 

[Chris1956]

Re: 1999 Johnson 90 Hp PLEEB Lagging, surging

Likely you have a clogged antisiphon valve, fuel tank vent, dirty fuel filter or some other fuel restriction. Pump the primer bulb and see if that fixes it.

 

[83mulligan]

Re: 1999 Johnson 90 Hp PLEEB Lagging, surging

pumping primer valve didn't help anything. I don't see an inline filter. Not sure how to check fuel tank vent other than blow out hose?

 

[Chris1956]

Re: 1999 Johnson 90 Hp PLEEB Lagging, surging

Does primer bulb collapse? If so, there is some sort of restriction upstream of the bulb. There should be a main strainer under the airbox. Maybe it has some dirt?

 

[83mulligan]

Re: 1999 Johnson 90 Hp PLEEB Lagging, surging

Chris, primer bulb pumps and returns to shape. I'll pull the fitting under airbox. Its made of white poly plastic. There may be a strainer in there.