1977 Johnson 140hp spark problems

[cvtech1]

My 1977 140hp Johnson seems to have an intermittent spark problem. I had it looked at and put on a spark tester and it was not getting spark on all 4 cyl. We took the plugs out and still not getting good spark on all cyl. We took the key/control harness of the motor that leads up to the controls and It starting sparking like crazy(good). So I was told it was something leading up to the key switch. Anybody have any idea what this could be? Thanks, and I do support iboats because of this forum it is so informative.

 

[mrcj001]

Re: 1977 Johnson 140hp spark problems

It could be the key switch itself......

There is a key switch test that can be performed

Its in the OMC service manual........

 

[R.Johnson]

Re: 1977 Johnson 140hp spark problems

It makes me wonder if your cranking RPM is fast enough. Did the cranking RPM increase when you disconnected the harness?

 

[cvtech1]

Re: 1977 Johnson 140hp spark problems

It sounded like it did but not too sure.I know it sort of struggles when trying to crank on 1 battery then speeds up after holding the key for a couple of seconds. I have a perko switch and have had to put it on 1&2 batteries and it cranked faster and started. It did not start the last time though.

 

[cvtech1]

Re: 1977 Johnson 140hp spark problems

It did get much better spark after disconnecting the harness.