Black Oil

[MAITOI]

I have a 2002 Yamaha 115 4 stroke. I change the oil every year or 50 to 100 hours. The oil always looks black. Is this normal? One boat dealer told me it was.

[JohnMickish]

There are two schools of thought on this and both have valid points. Oils have detergents in them to keep sludge from forming in your engine.

Theory one:

Black oil means the detergents are working and keeping the sludge from forming but why do you have sludge?

Theory two:

Clean oil either means you have no sludge to clean or the oil isn't doing it's job of cleaning.

Sludge comes about from the combustion gasses leaking past the piston rings. ALL engines leak combustion gasses into the crankcase, some more than others and age/miles/hours definitly contribute here. If you run alot when it's frigid out that lets more gasses slip by the rings. If you hammer the throttle when the motors cold that hurts too. We all know metal expands when warm so the rings seal better when the motor is warm. There are other factors involved as well but this is the major cause.

Now if you and your buddy both have the same motors, same hours, same driving style, same service interval, same filter and same oil and yours is black and his is clean maybe I'd talk to the dealer about it.

To sum it up, I wouldn't worry to much about it as long as you change oil the way you are supposed to and use quality oil you should be ok. Now if the oil turns milky then we have something to talk about.....

[SUNNYD]

Normal...I have a 2003 Yamaha 115 4-Stroke and everytime I have changed it, the color is much darker going out then when it goes in...Mine has 3 years of service on it and it has been flawless...the only thing I have ever done is change the oil, gear case oil and oil filter at recommended intervals and I just got around to getting new spark plugs in last week. She is ready to go for this year!

Take care!

[musky hunter]

Oil is black with 50 hrs? Any chance that cooling water is leaking into the cylinder? That seems odd to me. Depending on your brand of oil, you might be able to send a sample in to them and have it tested for contaminants for free. That might tell a lot.

[marine_man]

I would think if there was water in the oil it would turn a milky color.... not get darker...

marine_man

[Jeremy airjer W]

Yup! looks like chocolate milk.

[JohnMickish]

Quote:

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Yup! looks like chocolate milk.

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But costs thousands per gallon!

If it really bothers you try a different brand of oil and make sure the cap is on tight and let it warm up good before you run like a scalded monkey. Also make sure the evaprative controls are all in good shape with no cracked or leaking hoses to the crankcase.