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Mercruiser Drive-Unit Oil Consumption

Tin Diesel

Tin Diesel

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I have a question for those of you with with a Mercruiser I/O (or for the motorheads out there) ... I am seeing some drop in the stern drive oil level. Is this normal?

Background: I bought the boat used last fall with low hours - it hadn't been used at all in the last 3 years. Soon after getting it, I saw that there were signs of leaking oil out of the water intake on the stern drive. I had the stern drive rebuilt (new seals) at 110 hours (back in December). A week ago, at 136 hours, I thought to check and the level was down to the "add oil" level. I filled it to the top line last week. This weekend we used it for 8.5 hrs. The fluid level dropped 1/4 inch. I see no sign of leaking oil on the stern drive (although she was in the water the whole weekend so it wouldn't have been able to adhere)
 
Did you see an oil slick on the water when it sat still? I had a bowrider with a Mercruiser I/O and I never had a problem with leaking oil or oil usage. Not sure how it would be used, has to be leaking still. That stuff is thick also like 80 weight as I recall. Check the fill screw near the bottom on the side of the drive there is an O ring on the plug there.
 
There should be no change in the oil level ever, if the level drops again there must be a oil leak some where, first be sure to check the oil resevore and hose first for a leak ( if equipped with a remote resevore) since you just had the outdrive re sealed. There must be a leak some where the outdrive does NOT use up the oil !
 
Yeah, great post! Thanks.
There was no sheen, and no residue at the water intake.

The biggest drop was after it was rebuilt, so given what I read in your post, that makes sense.

I think I'll watch it for a while before I worry too much about it.
 
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