1978 35 HP Evinrude - Issue at High Speed

[lake of two]

Hello - hoping someone can help me out. My 1978 Evinrude 35 HP motor recently developed an issue at high speed under load. Lower speed (under 2/3 throttle or so) or high speed in neutral, no issue. At higher speeds, the engine stops violently for about a quarter second at regular intervals depending on the speed of the engine (every 3 seconds at lower speed, at WOT, about every), shakes the heck out of the motor and the boat. Thought it was fuel issue, drained the float bowl (looked clean), fuel filter was clean, put new tank of premium in and also changed the plugs - no help. Starting to suspect its an electrical issue. If it was one of the coils, would think it would just get sluggish for half a second, not violently stop. Starting to suspect its the power pack? Any suggestions on alternate causes or how to diagnose the electrical issue much appreciated, THANKS!

 

[Cap'n Chaos]

Re: 1978 35 HP Evinrude - Issue at High Speed

Sounds like a lean sneeze.

 

[Watermann]

Re: 1978 35 HP Evinrude - Issue at High Speed

Coils are a very simple device and rarely just up and quit randomly. If the coils did do that you would have a definite miss all of the time. My experience with bad power packs has been that they will intermittently die off and you can't start it back up until it decides to work again after everything cools off. If it's the original power pack then it couldn't hurt to replace it, it could be just starting to go bad and killing power to the coil. My power pack always seemed to up and quit when it was at wot as well. Does it do the hiccup every single time at wot or randomly?

 

[lindy46]

Re: 1978 35 HP Evinrude - Issue at High Speed

If it feels like you're hitting an underwater obstruction, like a log, it's most likely a bad clutch dog or the shift lever is worn or out of adjustment.

 

[lake of two]

Re: 1978 35 HP Evinrude - Issue at High Speed

If it feels like you're hitting an underwater obstruction, like a log, it's most likely a bad clutch dog or the shift lever is worn or out of adjustment.

Thanks everyone for responses - just to clarify a bit, issue is not random - it happens every 3 seconds at about 2/3 throttle and every second or so at high throttle - i had a friend check the primer bulb when running and it was hard as a rock so no issue with leaking fuel line or fuel pump i suspect.

It most DEFINITELY feels like hitting an underwater obstruction so I suspect I may have to pull apart to take a look at the clutch dog, read a few other posts on this. I never have an issue with the motor kicking out of gear at any speed and shifting has always been really smooth., also didn't see any metal in the gear oil when i drained it last year so didn't suspect transmission as a cause.

A friend who's pretty good with outboards suggested it might be a loose armature as well so may check on that. Any other suggestions/ideas more than welcome, will advise what i find when i go to the lake in a week and a half. Thanks again.

 

[F_R]

Re: 1978 35 HP Evinrude - Issue at High Speed

Trust me, you are giving the classic description of a worn out clutch dog in the lower unit. Outboard mechanics hear the story 'bout every day. What is happening is it is coming out of gear, rotating half a revolution, and slamming back into gear--till next time. The more power you apply to it, the oftener it jumps.