86 Evinrude 70 hp runs rough...

[Millcreek1]

I have an 86 Evinrude 70 hp that runs rough, sometimes it will take right off at wot, then cuts out, surges, sometimes it just won't go at all, like it is running on only 1 or 2 cylinders. Idles OK. I just replaced the vro pump, diaghram deterioted, cleaned the carbs three times because of the rubber pieces , third time were clean, flushed out the entire fuel system. New spark plugs. Oil pick-up is disconnected, running on 50/1 premix in tank. I think it may be an electrical condition, CDI unit breaking down? I checked the coils & spark plug wires, all resistance readings are within specs. Motor was starting to surge before the fuel problem occurred. Any help would be appreciated.

 

[oldcatamount]

Re: 86 Evinrude 70 hp runs rough...

I would suspect a fuel restriction issue rather than an ignition issue. "Surging" is not usually ignition related. The rubber pieces from the bad pump are most likely the culprit. A tiny piece of debris can cause the symptoms you describe. My suggestion is to re-clean the carbs using a piece of fine wire to poke through the fuel passageways (that you can get to) and then blow them out with compressed air. Having said that, there may also be an issue with your fuel tank not venting correctly.

 

[Millcreek1]

Re: 86 Evinrude 70 hp runs rough...

Cleaned carbs again, remove floats, needle valves, blew everything out, no debris. New tank, bulb stays firm, pumped while running, no change. Motor revs to full throttle then cuts back to about 1/3 throttle like there's a govenor, cut out or something. Bring back to idle, rev up, does the same thing.

 

[oldcatamount]

Re: 86 Evinrude 70 hp runs rough...

How about the operating temperature? Do you think it's running hot, and can you see a good pee stream of water coming out?

 

[Daviet]

Re: 86 Evinrude 70 hp runs rough...

Just to eliminate a problem, use an inductive timing light to check the spark on each cylinder to see if you are dropping a cylinder. That will tell you if it is a fuel or spark problem.

 

[Millcreek1]

Re: 86 Evinrude 70 hp runs rough...

Good stream out of the pee hole & I will try the timing light.