1976 75HP Evinrude, dies under load.

StickyWidget

Seaman
Joined
Aug 2, 2011
Messages
72
Model 75643D

Runs on muffs and in a bucket.
Dies when put into either forward or reverse in the lake.

Compression is 115-120 on all three cylinders.
Spark jumps 7/16 gap.
New spark plugs installed. (Gapped to .03, Just read should be .04, is that correct?)

Seems to idle high but I don't have a tach yet. (If I lower the idle by adjusting the screw it dies)
Sporadically while idling on muffs I did notice RPM change without moving the controls. Only once or twice. I think it went up in revs once and down once.

I did get it to move the boat forward at a very slow speed for maybe a minute but as soon as applied more throttle it died.

I took the carbs apart today and didn't notice anything that I would think clog them, (My first look inside a carb) One of the carbs had no gas or very little in it when I pulled it. I think the needle was "stuck" on the seat. I don't have rebuild kits so it was just dismantling them and blowing air from a compressor through everything I could.

After I put the carbs back together, I inverted them and in one orientation they let in air, the other they didn't.

I have not ran it after the carb "work" but judging by the lack of gunk and debris in the carbs I doubt it would have fixed anything.

I was told this engine was running on the water last year.

I believe I read that the high and low speed jets are not adjustable without replacement. What would cause an engine to not idle lower?

Would no fuel or little fuel to one carb not allow acceleration under load but still idle and accelerate on muffs?

Any clues as to what is causing this and what I can check to try and fix it?
 

Daviet

Fleet Admiral
Joined
Sep 24, 2008
Messages
8,958
Re: 1976 75HP Evinrude, dies under load.

Those engines would run and sound pretty good when running on two cylinders on a hose, but would not work very well when in the water. You said one carb had little or no gas in it, could be your problem. If you have good spark and compression, you should propbably think about properly over hauling the carbs with new gaskets.
 

StickyWidget

Seaman
Joined
Aug 2, 2011
Messages
72
Re: 1976 75HP Evinrude, dies under load.

I got it to work!!!! Seems a stuck needle was the problem.
 
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