Coil Problem??!!??

[newtong_ware]

Here's a question for you guys. Can 1 bad coil cause problems on 2 cylinders?<br />I had some issues getting the motor (115hp johnson 1976) to run right. I wasn't sure if I had a problem with the power pack or the coils. And I still am not real sure.<br /><br />After doing a few things with the electrical and such and rebuilding the carbs I cranked up the boat. I had to work real hard to get it to crank by the way. (This is why I have been working on it in the first place).<br /><br />It just did not seem to be running very good. I checked for spark and found the two port cylinders not getting any spark. I got online and checked on a few things and priced some coils and power packs and went out to check further a few days later.<br /><br />After getting the boat cranked, I checked each plug lead with a timing light while idling.<br /><br />Bottom port cylinder was not showing anything, and I had a good light on other three. I swapped the plug and coil wires between the two port cylinders and now neither would spark.<br />I put them back to the original position and got back to all three except the bottom port cylinder indicating fire.<br />I swapped the bottom port coil for the bottom starboard coil and then both starboard cylinders looked dead and both port fired.<br /><br />Once again, how can one bad coil cause either one or both cylinders in one bank to fail. Is this a coil issue or a power pack/coil combo issue?<br /><br />I thought about just getting all four coils and the power pack and shotgunning the problem, but I had much rather try and understand exactly what is going on as part of the learning process (as well as saving a few dollars).<br /><br />Any ideas?

 

[WillyBWright]

Re: Coil Problem??!!??

Actually I think you have a bad power pack and one bad coil. Take a close look at the insulation over the coils. I'll bet there are a few cracks. The cracks let moisture in and corrode the windings. If the cracks occur bewtween the coils and the laminations, spark leaks out there instead of going to the sparpkplug. The best approach is to shotgun it. If one coil is cracked, the others are or will. Try those before getting the pack, but I'll bet you need that too.

 

[newtong_ware]

Re: Coil Problem??!!??

yep, just ordered a couple of coils and a ppack.<br /><br />I did read that any voltage (DC) on the blk/yel kill switch circuit is a bad thing. I read about 25 millivolts. This seems too low to matter to me. What do you think?<br /><br />This engine has whipped me since I first got it. It has always ran hot and cold. Sometimes it just won't crank. Other times it is fine. Sometimes it will crank but barely run, and then when it does crank and run good it is soooo sweet. It will nearly throw you outta the boat when you give it the gas when all is right. Maybe I have been chasing coil and ppack problems all along and just did not know it.<br /><br />As always, Thanks for The Help!

 

[MCM]

Re: Coil Problem??!!??

I had a similar problem on a 1975 motor, it was temperature sensitve, above a certain ambient temp and it had spark and would start below that and nothing. Drove me about nuts, replaced the coils which were cracked, didn't help, replaced the p/pack and same thing. In the end it turned out being the timer base was going/gone out. Hopefully that won't be the problem in your case.<br /><br />Just keep troubleshooting and you'll locate the problem.<br /><br />Here's a link to a site with alot of good info on ign. troubleshooting. web page<br /><br />Good Luck