'72 mercruiser ignition coil problem

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I just bought an older mercruiser (ford 302). On first trip out it died after about 20min. After some testing I narrowed the problem down to no spark from the coil. After a tow back to the launch, I replaced the coil (generic coil from autozone). Next time out it ran fine for about 30min, until I idled back. It died and would not start. The coil was slightly warm (~150F), so I pulled it off and dipped the sealed end into the water. Put it back together and it ran fine (at least back to the launch). Any thoughts of what to check before the next outing? Would the coil be over heating? It has the in-wire resistor, when I tested w/ key on it was ~9v. With motor idling I found ~11v at + terminal. Any advice appreciated!

 

[coastalcruiser]

Re: '72 mercruiser ignition coil problem

welcome to iboats!

I had a 302 coil in my boat eXplode! I was a chrome high discharge one and had oily stuff all over and burned up pertronix points what a mess!
I went out and got a basic ford truck coil, and some new pertronix.
worked fine but later on learned here that marine coils are epoxy filled.
I noticed the engine ran better without the resistor.
if you do a tune up, new points condenser, new plugs, wires, dist cap, rotor i'm sure that will help.
you will need a timing light, dwell meter and feeler guage.

 

[coastalcruiser]

Re: '72 mercruiser ignition coil problem

just did a google and learned that pre 1975 there was a ballast risister, because if your using points, in my case i had pertronix electronic ignition and then its not needed

maybe you need to check connections like ground and make sure your using new points etc.
I also searched old posts and there is lots of good info there.
hope this helps
Rob

 

[leaf]

Re: '72 mercruiser ignition coil problem

Thanks Rob! I will reviw the old posts, and probably try a tune up.

Being stuck out on the water for 1+hrs was not a good introduction to boating. I tried to tell the kids it was an "adventure", but they didn't buy it.
LF

 

[jw2101]

Re: '72 mercruiser ignition coil problem

I just bought an older mercruiser (ford 302). On first trip out it died after about 20min. After some testing I narrowed the problem down to no spark from the coil. After a tow back to the launch, I replaced the coil (generic coil from autozone). Next time out it ran fine for about 30min, until I idled back. It died and would not start. The coil was slightly warm (~150F), so I pulled it off and dipped the sealed end into the water. Put it back together and it ran fine (at least back to the launch). Any thoughts of what to check before the next outing? Would the coil be over heating? It has the in-wire resistor, when I tested w/ key on it was ~9v. With motor idling I found ~11v at + terminal. Any advice appreciated!

I had the same problem last year. I removed the in wire resistor and bought a coil for around 55.00 that has resistance and fixed it.

 

[leaf]

Re: '72 mercruiser ignition coil problem

Since i have the in-wire resistor, if i bought a coil w/ resistor would i need to run a new wire (to keep from droping the voltage to much)? where does this wire originate from (pardon my ignorance)?

 

[jw2101]

Re: '72 mercruiser ignition coil problem

I had the same problem last year. I removed the in wire resistor and bought a coil for around 55.00 that has resistance and fixed it.

 

[jw2101]

Re: '72 mercruiser ignition coil problem

No you shouldnt have to. When a resistor starts to go bad it can work and stop working at any time. The wire should be directly of ignition switch.