Milky exhaust on a 2010 merc 40.

[sled59]

I took the boat out after fishing yesterday and noticed that where the exhaust leaves the motor it oily with a milky look. The motor runs great. Hoping that everything is ok as fishing season has been great and I don't want stop yet.

[CAMAN]

I'd first pull all the sparkplugs and make sure they are clean and firing properly.

Also check your oil and see if it is of proper level and clean.

[sled59]

I did check the oil and it was perfectly clean and full.I will pull the plugs and check them too. The funny thing is it was running great.

[CAMAN]

I guess I forgot to tell you to also check the lower unit lube. And while you're down there pull the prop and make sure there is nothing wrapped around the shaft damaging the seals.

[Hoey]

The milky look is typically associated with moisture, either in the fuel, oil, etc...

[delcecchi]

Is this a 4 stroke? If it is a two stroke, I would say that is pretty normal. The exhaust has water and oil in it. The water is mixed in to keep upper part of exhaust cool. Oil from the gas. Sometimes looks milky, depending on how you run it.

Four stroke shouldn't be oily.

[CAMAN]

He said 2010 Merc, from my memory Merc stopped making 2-strokes around 2005'ish? So I kinda assumed it was 4 stroke.

[sled59]

I checked the lower unit lube and it looked fine. I did change it and also pulled the prop and there was nothing behind it.

[CAMAN]

If everything looks fine with no abnormalities, then I would say it is just a symptom of the cooler weather and water not allowing the motor to get fully up to operating temperature and preventing the motor from burning everything off as efficiently.

One possible issue, although with the motors age it is unlikely, is the thermostat could be stuck open and not allowing the motor to warm up at all. A good test is to go out and run the motor for about 10 minutes to get it up to temp, shut it off, take off the cover and place your hand on the block. If you can hold it there for more than 3 seconds then I would say the motor is running too cold.

[sled59]

Caman,I called the marine we bought the boat at and you are right on the money. He asked if I had been trolling alot that day. Thats all we did since the speed limit is only 10mph and the fish were biting while trolling. Cold water and not getting the motor up to temp.

Thank you

[CAMAN]

Excellent! One tip if trolling all day is when you're about to head in, run around the lake, at or around WOT for 5 minutes or so to clear the cylinders and exhaust of the built up carbon and other gook that got built up during the day. But I guess that is kinda hard to do when you are limited to 10mph.

[sled59]

Caman,

Thank you very much for your advice. Most of the people on here are great to get opinions from.

Thanks again.