Bottom end of Stern drive mystery hole in the casing ?

Cheech75

Cadet
Joined
Mar 28, 2020
Messages
9
While preparing to re-install my 1982 pre-Alfa stern drive, that has been hanging from a cherry picker (engine puller hoist) for the last two days.
I noticed a small round spot of gear oil about the size of a half dollar on the floor, looking up at the lower end, i see a very small perfectly round 1/8" hole about the size a BB, the casing showed a slight sweat like leak, but not a dripping or oozing type of leak, more like a very slow sweat like leak. Guessing when the gear lube gets thinned out from being used it will then run out sure in no time if not plugged.

This small BB size hole is in the casing on the opposite side of the gear lube fill screw approximately 3" higher then the fill screw on the other side.
I had stuck a small thin screw driver blade into the hole that went in about 3/16 and came out showing very clean gear lube of which I had drained and re-filled the leg about 4 days prior to pulling the leg and hanging up-right by the cherry picker, while waiting for delivery of a new alignment tool shaft and new gimble bearing. Then I can retire my sledge hammer (read back about 4 days for that story) anyway, is this hole suppose to be their and is it missing a push or screw in type of plug. I dont think so, but if so then what is this mystery small hole for, anyone know before I just plug it with perhaps JB weld.
 

Fun Times

Moderator
Staff member
Joined
May 16, 2009
Messages
9,241
Hi there, sorry to see your stern drive has developed an gear lube oil leak.

That hole you found is going to be for the stern drive water drain cavity and it needs to be there...Since you have oil coming out, there could be a small number of oil seals of different locations that may have gone bad inside the stern drive. The following link are of some ideas with photos of what could be wrong for you to start out with, http://www.mercstuff.com/loweroilleak.htm

You could first try pressure testing the oil cavity side of the stern drive to see how bad of a leak you've got there and may help you narrow down what area the leak is occurring from...Then re-pressure test after the new seals are installed.

Hope it's one of the easier ones to repair for you, good luck.
 
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