#2 cylinder has erratic spark.

**bhgammon** · 07-04-2016, 07:53 AM

Have changed plugs - no improvement. Have swapped spark coils - problem remained with #2 cylinder. Checked for broken wires - found none.

Spark varies from almost steady to intermittent. Running boat reaches near max RPM and slows back and forth.

Any suggestions please?

**Cray** · 07-04-2016, 09:03 AM

It might help if you would tell us what motor,size and year. So many variables in ignition on different motors. Just off the top of my head I'd say you got a black box in the ignition system going bad.

**bhgammon** · 07-04-2016, 09:19 AM

Name: Evinrude 55hp tag.jpg
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!979 Evinrude 55 HP Mod 55979C Ser # E0006271

**Cray** · 07-04-2016, 10:59 AM

On those you should have a black electronics module on side of motor ( think it was actually called an ignition module ) with wires running to and from it. Should have one or more going to coils. My bet is it is going south on you. I don't know any way to really check it. Usually when they start going out it will run fine when cold but as motor warms and box gets hot it will start to break down causing a miss fire. Hopefully Sliderman will see this and chime in. He is really sharp on this kind of stuff. I just know from experience back in the mid 70's those boxes went bad on a regular basis.

**bhgammon** · 07-04-2016, 01:54 PM

Thanks for sharing your knowledge, I was thinking along that same idea except it seems to run better as it heats up. I still need to check all the wires real good. This motor has had several wires that moisture had gotten into and the copper had deteriorated to near dust. Every time I find one that is questionable, I replace it. I really need to try to find some replacement harnesses and get it over with. I had the cylinders re-sleeved 3 years ago and the engine is in top shape so I guess it would be worthwhile to overhaul the electrical system too.

I don't think it would be possible to switch the ignition wires on the ignition module to see if the problem moves to the #1 cylinder because that probably would reverse the timing (not a smart thing to do).

Bruce

**wannabe fisherman** · 07-04-2016, 02:06 PM

on a 100hp '80 'rude there are 2 of those modules, I had 1 go bad and the motor ran about half throttle and wouldn't shut off. I had to pull all the plug wires. they'll do strange things when they go bad

**Cray** · 07-04-2016, 09:31 PM

Originally Posted by bhgammon

Thanks for sharing your knowledge, I was thinking along that same idea except it seems to run better as it heats up. I still need to check all the wires real good. This motor has had several wires that moisture had gotten into and the copper had deteriorated to near dust. Every time I find one that is questionable, I replace it. I really need to try to find some replacement harnesses and get it over with. I had the cylinders re-sleeved 3 years ago and the engine is in top shape so I guess it would be worthwhile to overhaul the electrical system too.

I don't think it would be possible to switch the ignition wires on the ignition module to see if the problem moves to the #1 cylinder because that probably would reverse the timing (not a smart thing to do).

Bruce

Bruce, please don't swap the wires

you may be on to something with the wiring though. I would take the time to check it all real good first.

**sliderman** · 07-05-2016, 07:05 AM

Your mention of the condition of the wiring is probably significant to the problem. In most cases, the wiring is corroded to the point that the stator and timer base require replacement. Which will make for an expensive repair. There remains a strong chance that the power pack is at fault but it sounds like there is a high probability that the pack is not receiving the signal to fire all cylinders. You may be money ahead to take it to a shop and have the system tested.

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