merc 120 sterndrive gear oil

[paulages]

hi all,

i'm new to this boat... well, all boats to tell you the truth, but i'm a car and motorcycle mechanic, so i'm not totally clueless.

that said, i just bought a 1968 fiberform continental hardtop, with a mercruiser 120 I/O. i took it out for a few outings, after having done a tuneup on the inboard and doing a water pump rebuild on the outdrive. it ran great for a bit, but developed outdrive problems this weekend.

what i didn't do was check the upper/lower oil. i know, stupid. the gears in the upper are fried... lesson learned. what i've read on here is that the upper and lower gears share oil and therefore if one is fried, so is the other. however, the manual reads:

"On models prior to approximately 1973, the two reservoirs are independent, and must be drained separately."

So my question is: is my lower fried too? I will be pulling it tomorrow and checking the lower oil, but it's pointless if they do in fact share oil and i should be looking for a replacement outdrive.

 

[Jake_MN]

I have no experience with this model, but I suppose the first thing I'd do is drain the lower unit oil. If you torched the gears I would expect to see metal in the oil when you drain it. Either way I'd definitely say it's worth pulling and inspecting the lower unit. It's not a ton of work to get a look at the gears and it could save you a lot of $$.

 

[vahandyman]

only fried if you ran it with no oil in lower unit. when you changed the pump did you not have oil leaking from the upper gear case?