1975 Evinrude 135 idle surge

[Cynic]

Hi again everyone,

Well I got the manual, took off the lower unit and the water pump was missing 3 blades. Changed that. Pulled the carbs and rebuilt those. Pulled the fuel filter and the screen is perfectly clean. Changed plugs. The engine cold started relatively easy. Hold choke, fire and gas it a couple times and hold RPM steady until slightly warm and then it idled without dying.

The question I have is, the motor will jump in RPM for a second or two and then drop back down. Does anyone have any idea if this is normal for this outboard or if there's something I overlooked and need to go back and check? Thanks for your help, it's been priceless so far!

Ben

[flabum1017]

Could be that a cylinder or two is not firing then the "surge" it the cylinder or two catching.........

did you find all the pieces of the old impeller?

[Cynic]

Could be that a cylinder or two is not firing then the "surge" it the cylinder or two catching.........

did you find all the pieces of the old impeller?

Previous owner had boat for 8 yrs and never changed it. I found mushy bits of rubber inside and removed everything.

When I bought the motor compression was 140-140-140-132 so I know one is a little lower. Being that is was within 10% I figured it was just fine. Running premo gas so I know that isn't the issue. I'm assuming that since the impeller wasn't working properly that the top left cyl (#2 I think) was getting too warm and that's where i'm losing the compression.

It never dies when it's idling like this. I left it run for like 10 min and it would just occasionally blip like that.