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1983 70hp - weak spark in top cylinder

N

new_boat_guy

New member
Hey guys,

I just bought a 1983 70hp Evinrude. When on muffs the motor runs okay but sounds like it is hitting on 2 cylinders and once in a while hits on the third. When I put the boat in the water it sounds like it has a low idle speed and when i kick it in gear and give it a little throttle it sometimes dies (usually on first attempts after sitting for awhile) I can never put it in gear and punch it to full throttle or it will for sure kill it. It has to have a gradual acceleration to get to full throttle. When I can get it up to full throttle though it runs like a top. On the muffs however I can punch it to full throttle when in gear and have no problems.

The motor sat for 3 years before I bought it so I pulled the carbs and cleaned the jets. This didn't solve the problem.

I checked compression and have an even 70 psi across all three.

I pulled out all 3 spark plugs, connected them to the coils and turned the engine over, while holding the plug about 1/2" from the block. The top spark plug has weak spark and does not show the bright blue spark like the others.

This is not my video but my engine sounds exactly like this when pulling the connector off the spark plug.
https://www.youtube.com/watch?v=Z3D8i0gLu8o

I bought new spark plugs and this did not solve the issue. I swapped coils around with no luck.

I am wondering what my next step should be. Some things I read say the power pack will NEVER produce weak spark, either good spark or no spark. Is this true? Some say the stator may be bad or the timer base trigger?

Any suggestions would be greatly appreciated.
 
On muffs and in gear is still NUETRAL.-----The prop does no work moving air !!!----Test compression with another gauge.----70 PSI is nowhere near what it should be.
 
Compression at 140 psi is ideal.

Check stator visually to see if it might be dripping a sticky substance down on the powerhead area. If so, the stator is in a meltdown stage and requires replacing, HOWEVER... a failing stator will NOT affect just one cylinder!

Cylinders are marked from top to bottom as 1,2,3.... Switch the wires from the powerpack to #1 & #2 coils temporarily to see if the weak spark transfers to #2 coil or remains at #1....... I know you said you switched coils... humor me. No luck indicates, to me, something about the gal I met at the local tavern last night! :)

If #1 remains weak = bad coil.

If weak spark transfers to #2 coil = Bad powerpack "OR" perhaps a poor connection between pack and coil "OR" pack & timer-base (pin & socket connection within rubber plug).
 
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Thanks for the thoughts joereeves. I tested spark again by sticking a screwdriver in the spark plug socket (better spark than I previously thought), blew out the jets again, and took it to the river to test. I tried starting it but it would run for about two seconds then die. I then adjusted the idle screw so it would idle at a higher rpm. This seems to have solved most of the shifting and take off problems. There is still a little lag when I go from no throttle to full throttle but for now that may have to be an issue for another day. Thanks for the help!
 
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