Loss of spark after 15 min on the water

Poontanker

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Jun 11, 2019
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I have a 05 3.0 Mercruiser that has electronic ignition. Out of storage for the first time this year, boat started esasily. After 15 min and 4 or so miles out of the marina, the engine just died, like someone shut off the key. No effort could get it running. Got towed back in. Suspecting ignition problems, I tested the lanyard/emergency switch. Good continuity there. Did some research and tried to see if the coil was bad, but my limited skills with a multimeter proved inconclusive. So, for a few bucks, I bought a new one and the boat fired right up. Great, I thought.
a few days later, back out on the water again and at the same 15 min later, it died again....same way as before. Got towed in again. Put the boat away. Back out to boat today, I did absolutely nothing to the boat and hit the stater. It fired right up. Hitched the boat to the truck and took it home where I hook up the hose, hooked up a timing light to the coil and started it up. Also started my timer. Sure enough, after about 15 min, she died. And again no relight was successful. Noted that the timing light was no longer flashing indicating no spark. It's been just about an hour since it last died and still no spark.
Thoughts?
 
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