Engine Stopped. Electrical??

We were crossing Lake Erie this morning when our engine stopped as though the key had been switched off. No sputtering, surging or anything, just stopped. Tried starting it a couple of times, turned over, but no go. Stopped to get the anchor down as we were being blown into a rocky area. When I finished that, I tried starting the engine, and it started right up. Thoughts? I'm thinking an intermitent failure of the shift interupt switch or ignition switch. Should I just change these out? Anything else I should be looking at? Obviously, it's an intermitent problem and could be difficult to trace. After it started, the boat ran fine, and we've had no other issues all summer. The engine is a 1970 Mercruiuser 140 hp inline 4.

 

This might be slightly better than a guess but not much.
We had a similar unit (not identical) that sometimes stopped abruptly. And almost always it was a little piece of something that got stuck under the float valve and flooded the carbureter. It's been so long ago that I don't remember if it ever cleared itself or not. Usually we had to pull the top off the float chamber and remove the offending particle. And then we were on our way again. We had very quick access to the motor and so could smell that it was flooded. Might not be what happened to you at all. Just thought there was an odd chance this could be it.
Cheers,
Gilbert

 

I suspect you are looking in the right places. It's likely an electrical problem if it just quit and then cranked back up with no remaining problems. If it has magnetic pickup type distributor, the pickup coil could have an intermittent open related to temperature or vibration. Other things in the ignition path like the spark coil can also cause this.

 

Thanks for the replies. Have gone through everything, checked all electrical, and changed out the fuel tank (original steel full of rust), fuel filter, and water/gas separator. Also have a new ignition switch. Seems to be running fine now. Starts quickly, runs smoothly, and idles well even when first started. We'll be back out next weekend for a fairly long run, we'll see how she does. Thanks again.