76' 135hp johny no start, no spark

[jpendergrass]

As the title states. I brought this boat home, swapped out the fuel tank and fired the engine up. Ran good, throttled up fast, on the ear muffs. The controls wouldnt allow the throttle to return, had to manually do it at the motor. So I got a sweet deal on a complete OMC control with harness and cables. The red plug had been cut, but I soldered her back together. I did a bunch of other stuff but nothing to the motor. Got ready to head out to the lake tonite and she wouldnt start. Cranks over good. Did a spark check....nothing. Or should I say it seemed to spark every so often, and then not at all.
So, I learned years ago that if you change something and then something dont work, it must be in that area. So how do I find out why I dont have spark? Where in the wiring harness would send spark? Please dont tell me its the ignition box. I dont know if I can find one tomorrow. I will say that when it did spark it was weak. But this engine ran great before I swapped out the control.
Please gentlemen, help quickly. My 4 day weekend is slipping by FAST!!!

Thanks - Jody

 

[emdsapmgr]

Re: 76' 135hp johny no start, no spark

The engine needs to be spinning at 200-300 rpm in order to make spark. If you have a weak battery or poor connections, the engine may not be spinning fast enough. Unlikely that your changes have made difference, but there are some things you can check. The engine ignition system is independent of the control box. Once the starter spins, it should make spark. You can unplug the big red plug under the cowling, jump start the starter and check the spark. It will spark and run without the control box harness-the engine just won't turn off. If you get good spark with the harness disconnected then you know the problem is in the harness. If you have no spark or weak spark still, then you probably have a problem with one of the ignition components: coils, stator, power pack, timer base.

 

[tashasdaddy]

Re: 76' 135hp johny no start, no spark

black yellow wire is the kill wire,

 

[jpendergrass]

Re: 76' 135hp johny no start, no spark

Can I leave the kill wire disconnected if that is the source of my problem?

 

[jpendergrass]

Re: 76' 135hp johny no start, no spark

I can see my weekend is shot. Disconnected black/yellow wire, had spark. Yay!!! Till i got to #2, no spark. Decided to reconnect kill wire, no spark. Okay, its the kill switch. Maybe, I thought. disconnected again to check and no spark on the first cylinder I tested, #3 I believe. So this no spark seems to be intermittent but #2 never showed any spark. I will say that this is on a 1/2" at best gap on the tester. What in the new/used harness could be causing this???

 

[jpendergrass]

Re: 76' 135hp johny no start, no spark

Swapped out ignition key switch and great spark on all cylinders except #2. It appears the #1 & 3 coils/wires have been replaced. Should I go ahead and replace the #2 & 4 coils/wires??

 

[ezeke]

Re: 76' 135hp johny no start, no spark

You need to have a kill circuit so that you can turn the engine off with the ignition switch.

The series requires 250 RPM minimum to fire properly - read your service manual. That demands a fully charged, powerful battery, good cables and clean connections.

The series has problems with grounding, especially the rack that holds the ignition coils. Make sure that the connections are clean by removing them and cleaning, not by looking at them. Loosen and clean the grounding straps that run to the cylinder heads.

If the ignition coils are cracked, swollen, discolored, or if the potting looks melted, replace them.

 

[jpendergrass]

Re: 76' 135hp johny no start, no spark

#2 coil faulty. Replaced and fire right up. This was after replacing ignition switch. I would still like to replace #4 coil but I got the last one in town. I'm headed to the lake and will get another coil ordered monday. Thanks all for their help.