1986 75hp mercury 4 cylinder ignition problems. no spark

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forrester4484

Recruit
Joined
May 25, 2017
Messages
3
I am new to doing my own repairs on outboard engines. I was out on the water WOT and suddenly my engine dropped to 50% power. Slowly from there I lost all my power until the engine eventually died. After a while I was able to get it going enough to putz back to the launch. With WOT I was basically trolling. Now I can not get the engine to start at all. The fly wheel cranks no problem. It sounds like it's just about to turn over but wont. I tested spark and I have no spark on my top 2 cylinders. I have replaced the stator, trigger, and rectifier. Still the same problem. I'm not good with a multi meter but willing to learn. Is there a way to check the switch box with a multi meter? Is that even possibly the issue. Could it be ignition coils. Please help.
 
CaptnKingfisher

CaptnKingfisher

Petty Officer 1st Class
Joined
May 14, 2017
Messages
269
Unlikely that multiple coils simultaneously failed but it's easy to test your coils even if you don't like multimeters.. I'm a johnson guy so idk if you have a powerpack (maybe what you call your switchbox) that distributes your spark, but if you do, swap your known good coils that currently get Spark with the unknown coils that aren't getting spark at the powerpack terminal. If what I just said doesn't translate to your mercury, then you can always just physically move your coils around, a known good coil for an unknown coil. If you still get Spark on that cylinder, then you know your coils are fine and theres something wrong with the timing or sensors.

Did you happen to inspect your flywheel key when you were replacing the stator and triggers?
 
F

forrester4484

Recruit
Joined
May 25, 2017
Messages
3
I could be wrong.... but i don't believe this engine has a fly wheel key. The shaft the flywheel sits on is splined and has small flat spot to line the flywheel back on.
 
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