'78 Evinrude 85hp

[iluvgear]

My '78 Evinrude 85hp is running poorly. It will not run at top rpms. Feels like it is bogging down. Occasionally it will surge and run smoothly. My suspicion is I am loosing spark to one cylinder. New fuel line/bulb, clean filter screen, and when it surges the power is instant, faster than throttle response. With the engine idling I tried wiggling each spark plug boot to ensure a solid connection. This had no effect on the engine, but the lower port side cylinder send a good shock up my arm. I did not see any arching. Could this be my problem? Thanks in advance for any advice.

 

[Backlash]

Re: '78 Evinrude 85hp

Hey iluvgear (I do too!), It might be worth a try to run the engine, cover off, in darkness to check for arcing. Based on your description of the symptoms, it does sound like an electrical problem rather than a fuel related issue. Could be something easy but then again............Let us know what you find out. Good Luck.

 

[ridiver]

Re: '78 Evinrude 85hp

Hmmm, our 1978 85 Hp Evinrude did the same thing. There was a loose wire. (we knew because it had been taped in place by a previous owner) We just pushed the wire back it for that cylinder, started getting a spark again , and off we were...<br /><br /><br />f<br /><br />

 

[pstewart]

Re: '78 Evinrude 85hp

I had a similar problem with my motor. The inside cover is covered with foam which is slowly falling apart into dust. I took the carbs off and cleaned them out. Turns out these particles were getting into the carb and clogging it up. Sometimes it would run OK, other times it wouldn't. Previuos owner had no air filter on it.

 

[Mod2]

Re: '78 Evinrude 85hp

Moving to Johnson/Evinrude forum.

 

[pennyanman]

Re: '78 Evinrude 85hp

Had the same motor on a 16 foot Whaler for years, and had similar experiences, in my case was a bad pulse pack on port side, and had failure occur 2 times on same side in 5 years. Otherwise the motor was like a Maytag washer,it ran perfect all the time.

 

[Walker]

Re: '78 Evinrude 85hp

Take off all the coils and clean the ground straps for each coil. Put a dab of dielectric grease on each ground and try it. Also check that both lower sparkplug wires are not shorting to the clamp brackets on the cowling.

 

[iluvgear]

Re: '78 Evinrude 85hp

Walker and pennyanman thanks for your responses to my question from two years ago! Somehow during the forum reorganization my question popped up near the top. It took me a while but I finally figured out that problem. A tiny pin hole corroded in the thermostat housing where the cooling hoses attach. Under heavy throttle water would squirt up into the foam isulation lining the cowl. Since the boat is always in conductive salt water, the soaked foam would sag onto the power head and cause the ignition to short out. Replacing the offending piece of the thermostat housing solved the problem. Coincendently, I have a much bigger problem now where the engine will no longer start. I would love to hear any suggestion on my current problem. "Trouble with '78 Evinrude 85hp" http://www.iboats.com/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=28;t=013764