1968 55hp Johnson spark issue

[ARFFMEDIC]

I have a 1968 55 hp Johnson that i am trying to get running again. The engine/boat was a family members that let it sit idle for many years. I have replaced the wiring,and have a new battery, it cranks over great, but while cranking it has no spark, but the second you let off the starter (key still in "on" postion), it starts to spark, and occasionally will even catch a cylinder. I bypassed the ignition key to the starter thinking that there may be some kind of short in the switch causing the igniton system to ground out, but i had the same results. With the key on, I can manually advance the flywheel and get spark, but again, not while cranking under battery power. Any suggesstions on where to look next would be greatly appreciated.

 

[jlax27]

Re: 1968 55hp Johnson spark issue

I think I might have the same issue. Did you ever resolve? I see no spark when cranking. A couple times the motor would fire as soon as I let off of the starter key.

 

[pilotmsp]

Re: 1968 55hp Johnson spark issue

Although you've probably found the reason for not getting spark by now, I thought I'd post what I found to fix this problem for others.

I was getting the same symptoms as they were. No spark until letting off the ignition switch.

There is a fix posted that places a diode in loop somewhere, but I found that a larger (higher amperage) battery fixed the problem easily. These engines are sensitive to having too low of an amperage. They simply wont start if they dont get the proper amperage/voltage to the power pack.

In my case I replaced the impeller, which put a higher load on the starter since the impeller was fresh in the housing. My previous battery only had 70 amps of starting capability. New battery 100 amps......

 

[oldrudedude]

Re: 1968 55hp Johnson spark issue

Although you've probably found the reason for not getting spark by now, I thought I'd post what I found to fix this problem for others.

I was getting the same symptoms as they were. No spark until letting off the ignition switch.

There is a fix posted that places a diode in loop somewhere, but I found that a larger (higher amperage) battery fixed the problem easily. These engines are sensitive to having too low of an amperage. They simply wont start if they dont get the proper amperage/voltage to the power pack.

In my case I replaced the impeller, which put a higher load on the starter since the impeller was fresh in the housing. My previous battery only had 70 amps of starting capability. New battery 100 amps......

Thanks for sharing that. I'm sure it will help others in the future.