Shutoff and Milky Sheen on exhaust

[cfergu22]

I have 2 separate problems that might be related.

Problem #1 happened 2 days in a row on almost the exact circumstances...

After a 5 hour motor a cruising speed I put the engine to idle about 1/4 mile from the dock to put fenders out, and get lines ready. It idled for about a minute then shut off. I could not get it to start back up by cranking. I was by myself so I couldn't check for spark, but I know I was not out of fuel. I docked under sail and about 20 minutes later the engine started right up without problems. The exact thing happened the next day.

Problem #2, Not sure if this is related.

There seems to be a milky sheen on the water when i'm idling at the dock or coming in under power. It might coming out all the time but I don't see it when we're motoring because of the turbulence in the water.

Any suggestions for what to look at systematically because overall the engine is running great so I don't want to start digging around and cause a bigger problem.

Thanks,

Collin