85 HP Ignition Problems

[captain413]

I have a 1973 85 HP Johnson SeaHorse that won't crank. For some reason it it getting intermittent spark on all cylinders. It will spark for a minute then stop and now it wont spark at all. The ignition coils are fine. Does anyone have any suggestions on where to begine diagnosing the problem. It has a new starter and battery and is getting good enough rpm's to make spark. Thanks in advance for your help.

 

[ezeke]

Re: 85 HP Ignition Problems

The engine has to be turning 300 RPM to get good fire.

Disconnect the rectifier. Use a fully charged battery and remove all of the spark plugs then set up a tester that will be able to be adjusted to a 7/16" gap - you can do that with something as simple as a dry board and nails, just make sure that the ground is solid and that the spark plug wires have good connections.

Here is a picture of one that is sold here at iboats.

If the spark is a sharp blue spark capable of jumping the 7/16 gap at 300RPM, then your ignition system is probably not the problem.

 

[captain413]

Re: 85 HP Ignition Problems

Thanks for the advice about the spark tester. I have a parts motor so I decided to swap out the powerpack and sure enough that was it. It was a shot in the dark but it worked and the motor is running now, but thanks again for the advice.

 

[ezeke]

Re: 85 HP Ignition Problems

Good for you. Now here's a tip: powerpacks dont usually die without help.

Bad or failing ignition coils kill them and voltage riding the black and yellow kill wires from failing ignition switches kill them. In some instances bad rectifiers allow battery voltage to reach them.