Johnson 1988 175hp ignition coil silicone cracking (replace or no)?

[Intoodeeep]

I have a Johnson 1979 235hp with Johnson 1988 175hp electronic and carbs. I am building a new engine as the old one had a connecting rod go through the block. While going through the electronics I have found one ignition coil that has a crack in the casing and needs to be replaced. I have two others that are questionable. I can't remember off the top of my head what they tested when I ohm-ed them but I think they both tested fine. I have two others that look great and tested fine and then immediately tested bad. I have heard that its not always accurate testing them like this. Regardless of the ohm test, The two in question have cracks in the back of the ignition coil in the silicone itself. One of them was brand new from CDI and only used for ten hours when my old motor blew. I have read all over the place that they need to be replaced when cracks develop in the casing. But nothing actually refers to the silicone in the back. The CDI has a hard silicone back and another one I have is a soft silicone type. I also have a third ignition coil that tested fine but it looks like the silicone has bulged a little. On the fourth ignition coil the silicone looks like either some chemical came in contact with it or it got to hot This coil tested fine as well. Its hard to explain but I can post pictures when I get home from work as I am at the firehouse today. So question one, are the cracks in the silicone acceptable or not? Question two, is it possible that the ignition coils are getting to hot for some reason? This might explain the silicone cracking on the new ignition coil and the other as well as the appearances of the other ignition coils I have described. When the motor blew it was running well. I had just completed the break in period per the instructions. (someone else rebuilt the old motor) It is possible a some of these ignition coils already looked like this prior to me getting them, I just don't remember. I know the easiest way is to just hook it all up and see how it runs once I finish rebuilding the rest of the engine in the next week or so. I am just trying to catch anything upfront especially if this is symptomatic of a problem. I did have to replace a power pack and the Rectifier on the old motor due to issues. Don't remember what they were as it was over two years ago. The rectifier is also the ones that are on the 1988 175 and not the ones on the 1979 235. I know this is a lot of info, but I wanted to make sure you got as much of the background story needed to help me figure out what is going on if anything is.

 

[ronward]

In my opinion, if those coils are in that bad a shape you may as well replace them because you might find that when you go to crank the motor you might have to troubleshoot your ignition system. I know you don't want to do all this work only to find it won't start. Also here is something you might wanna check into...the part numbers for the coils for those two motors do not match, I would want to find out for sure if they would even work right on a motor that calls for a different part number. One other thing I might add is have you compared the carbs for the two motors? I'm wondering if you put a carb designed for a 175hp on a 235 if it won't starve for fuel. Would hate to hear you melted a piston. I am by no means an expert but these are questions that I would want answers to if it were mine.

 

[boobie]

The only way you can properly test a coil when you find one with cracks in it is to take it to somebody that has a coil load tester for any high voltage leakage. It can still have cracks and not leak. An ohmmeter will tell you nothing.

 

[Bosunsmate]

Boobie any word on why this forums taking so long to get fixed?

 

[boobie]

Bosun, I've just about had it and started going else where. I'm going to send Toneeees a PM on Monday and see if I get any response. The IDIOTS should have left it alone. JMO.

 

[Bosunsmate]

Boobie, yeah i just dont get it, the most busiest season for people wanting to fix their boats on here and thus order parts and nothing is being seen to improve on this forum.
Im sure some of the kids i see kicking stones at the shop could fix these faults in a few hours. This is taking iboats well over a month and still not even one improvement.
Tell Toneeeees you aint the only one who is disappointed
They really need to write a proper update notice up the top not just -we will have one when it turns up...

 

[Intoodeeep]

Why are they cracking? Overheating or something?

 

[emdsapmgr]

A cracked coil is a probable possible failure. Replace the cracked ones. If they are newer, I'd see if they are covered under warranty. (Factory parts have a one-year warranty.) The older coils on your 235 all work the same as the newer two-part coils. As long as the older ones are intact, they will run fine. Just a difference in design. You can mix them on an engine.