mercruiser lower unit leak

jim tesno

Cadet
Joined
Jan 3, 2010
Messages
9
My boats about 3 hours away. Had new seals,etc over winter. Put inl ast week and ran fine. Friend calls and says he believes lower unit seeping grease (sheen on water, only boat there,etc). Going up this weekend to check it out. Plan to pull boat to check unit for milky grease but before I do--- unit has external reservoir. If there was leaking, would milky grease show up in reservoir or just in lower unit grease?
 

mr 88

Commander
Joined
Nov 3, 2010
Messages
2,123
You do realize that whatever excess grease was applied will weep for awhile . That would be my first guess . Usually water is drawn in to the lower unit when the outdrive is in gear , not when it's just sitting.
 

shrew

Lieutenant
Joined
Dec 29, 2006
Messages
1,309
My boats about 3 hours away. Had new seals,etc over winter. Put inl ast week and ran fine. Friend calls and says he believes lower unit seeping grease (sheen on water, only boat there,etc). Going up this weekend to check it out. Plan to pull boat to check unit for milky grease but before I do--- unit has external reservoir. If there was leaking, would milky grease show up in reservoir or just in lower unit grease?

There is grease and there is drive lube. If water were mixing into the drive lube it would settle at the bottom of the unit since oil will rise in water.

1) Haul the boat
2) Let it sit for the day
3) remove the cap to the overflow reservoir
4) place an oil pan below the outdrive
5) remove the lower oil drain plug. (watch carefully)

If water seeps out first, you have water in the drive. Once the drive is flowing straight drive lube, replace the lower drain port and fix the seals.

If there is no water, then replace the lower drain port and check the drive lube overflow reservoir. If there is still oil in the reservoir, then backfill the oil through the reservoir.
 

achris

More fish than mountain goat
Joined
May 19, 2004
Messages
27,468
Once the boat's out of the water, check for water in the drive OIL (not grease). If you suspect a leak, then drain all of the oil out and do a pressure test (if the drive is gen II, you'll need to remove the drive from the boat before the pressure test. If it's gen I with a monitor, disconnect the monitor and put a plug in the hole)...

Chris...
 

jim tesno

Cadet
Joined
Jan 3, 2010
Messages
9
Thanks for the advice guys. I do intend to pull the boat but I was curious if the external reservoir might give me a clue first
 

achris

More fish than mountain goat
Joined
May 19, 2004
Messages
27,468
Thanks for the advice guys. I do intend to pull the boat but I was curious if the external reservoir might give me a clue first
Unlikely. Water is heavier than oil, and the monitor is higher then the drive. You have to get a LOT of water in the drive to see any water in the monitor. About the only thing a monitor will show you is if you're losing oil.

Chris....
 
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