Question on Very Old stern drive

[CraigBarnard]

I have what I think may be an original mercruiser stern drive and the upper and lower gear oil oil chambers are two separate chambers.
When I checked the upper chamber this afternoon (after draining the lower) I heard air being sucked in as if it where under a vacuum.
I decided I should remove the top cover and have a look inside. The upper chamber was empty.
I was wondering if anyone knew of a common cause for this to happen.

Thanks

 

[GA_Boater]

Craig - The guys in the Mercruiser section might be able to help you a bit more. They will probably want serial numbers. Good luck.

 

[Watermann]

Normal to have that happen. it's one cavity, the bottom hole in the gear case is the drain/fill hole and the top one in the upper is the vent hole. Just like on an OB you fill from the bottom and oil runs out the top hole.

 

[Fishermark]

Normal to have that happen. it's one cavity, the bottom hole in the gear case is the drain/fill hole and the top one in the upper is the vent hole. Just like on an OB you fill from the bottom and oil runs out the top hole.

I could be wrong.... but I believe the very old outdrives had two separate gearcases - an upper and lower. Each had its own fill and vent. A little more research is probably a good thing.

 

[CraigBarnard]

I could be wrong.... but I believe the very old outdrives had two separate gearcases - an upper and lower. Each had its own fill and vent. A little more research is probably a good thing.

Thanks I believe they are two separate chambers as well. the newer ones have a single chamber as Waterman suggested.
My outdrive has two fill holes and two level check holes on the upper and lower sections of the drive.

 

[79Merc80]

Pictures??

 

[Bt Doctur]

from manual 1 , does list 2 amounts of oil