Lower Unit Oil pretty dark...Problem????

SeaKaye12

SeaKaye12

Lieutenant Junior Grade
Joined
Jul 3, 2005
Messages
1,107
Hi,<br /><br />I drained the L/U today on the 1977 Merc 850 that I'm re-newing.<br /><br />It looked pretty black...kinda like oil from the car when it needs changing.<br /><br />I think I remember someone here saying that black L/U oil was a sign of overheating? True?<br /><br />Should I be concerned? The engine's been setting un-used for 25+ years... As far as I know from the previous owner...there were no problems with the L/U...<br /><br />Thanks for reading, Chuck
 
AMD Rules

AMD Rules

Lieutenant Commander
Joined
Sep 23, 2004
Messages
1,707
Re: Lower Unit Oil pretty dark...Problem????

Not a lot of value trying to evaluate oil that has been sitting for so many years unused. You don't have much to go on regarding how long it had actually run on that oil either. <br /><br />Inspect it for metal shavings, do a pressure test on the lower unit (if you wish), use new screw gaskets, refill it & go. Check it periodically between the first few trips by loosening the drain screw only enough to allow a few drips out. If no water is evident, and the color is fine... close it up for the season & go boating!
 
Z

ZmOz

Captain
Joined
Aug 13, 2003
Messages
3,949
Re: Lower Unit Oil pretty dark...Problem????

I wouldn't worry about it too much as long as there are no metal shavings in it. You may want to change it again after only a few hours use with new oil though, to help flush out all of the old oil. I don't see how a lower unit could possibly overheat, seeing as it's completely submerged any time it's doing any work...
 
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