misfiring 140hp

[marclee]

Hi all<br />I wrote a few months ago about a problem with my 140hp 1997 johnson v4 that from time to time lost power and sounded as if it was runing on 2 cylinders. I thought I had found the problem that one of the coil wires were shorting out however that was not the problem. since then I have had the carbies overhauled and serviced a new power pack fitted and have tried various coils all to ne avail. My last resort is the trigger which sends signal to power pack. can some one please advise on anything else it could be. My service guy is as stumped as i am. PLEASE HELP.

 

[rodbolt]

Re: misfiring 140hp

hello<br />on a case like that I hook a CD-77 meter on the top coil primary terminal and run till it misses. if the primary voltage remains stable on both meters retest with the bottom two coils. I alsoindex the flywheel making TDC and timing marks on the flywheel for cyls 2,3 and 4. check timing for cross fire while testing coil primary voltage. if the meters remain stable and the timing tests ok you just eliminated the ign system. if it does not pass its time to rerun the voltage tests on the pack inputs. its a process of elimination. sometimes time consuming but not bad. especially if you have a test wheel or a dyno to assist. but without chunking parts at it its the only way to test the system.

 

[marclee]

Re: misfiring 140hp

Thanks for the advice rodbolt. I will try it this weekend and let you know what happens.cheers budda