1976 Johnson outboard 9.9HP 10R76H diagnosis

[oldboatbuyer]

This motor worked great fort he first half of the Summer.
Started right up, ran great.
A month ago me and my son took the boat out, motor was fine.
Fished for about 45 minutes and went to look for a new spot and motor wouldn't start.

Changed spark plugs
checked fuel filter for any clogs
Replaced fuel line and bulb

Will not start.
Any ideas? I was thinking maybe the ignition coil?
Looking for some guidance or further diagnostics before I start throwing parts at a 40+yr old motor.

 

[racerone]

Step #1 is a compression test.----No point throwing beer tokens ($$$ ) at a worn out motor.----Does spark jump a gap of 1/4" or more.----Check the flywheel key.----A sheared key means no spark condition.-----Test driver coil.----Clean breaker points and recheck for spark.

 

[F_R]

Much has been written about those motors. Just for laughs, try a NEW set of UL-81C plugs. You'll need them sooner or later, anyway.

 

[OptsyEagle]

Put a few teaspoons of pre-mix gas into each cylinder, put the the spark plugs back in and pull on the starter a few times. The motor will either start and stall, once it burns through the gas. Start and run fine or you will get no response from it at all.

If it starts and stalls you most likely have a fuel delivery problem. Either a defective fuel line or fuel tank, a dirty carburetor, bad fuel pump, air leak, fuel line connector problem or dirty fuel filter, etc.

If it starts and runs fine you have a starting problem, most likely coming from the choke. Perhaps a couple other things.

If it starts and stalls once it burns through the gas, you just gave it, you have a spark or compression problem and will need to check the compression numbers and you will need to see if the spark can jump a 1/4" gap using an external spark tester. 3/8" gap is even better.

Let us know the result of the fuel test and we can advise you better from there.

 

[flyingscott]

Check the points and condensers. Also check the kill switch

 

[bktheking]

Check for spark- step one. Do you have spark?