Mercruiser 377 Duo prop

A friend of mine has a 2002 25' Colbalt with a Merc 320 hp, 377 CI Duo prop I/O.
I winterize the boat for him. This year when he went for his first ride his alarm for the gear oil went off. The resivor was empty and it is leaking from the bell housing. We have followed the line from the tank to the back of the engine and it is not leaking. It appears to be leaking from some where inside the engine. I know nothing about these engines. I thought you filled the lower unit like an outboard. My winterization has only consisted of draining and filling with anti freeze. He has never changed the gear oil or the engine oil as long as he's owned the boat.

Anyone have an idea what the problem is?

Riley wrote:    He has never changed the gear oil or the engine oil as long as he's owned the boat.

Please tell me he hasn't owned the boat very long... that is no way to treat a lady..

Joe, the majority of boaters are clueless, i was on a Master 197 2 weeks ago, I asked the guy what engine he had and he had no fckin clue what it was let alone even checking the oil on it, i lifted the lid and yes it was a Chevy. but the thing that really killed me was he had water in the bildge right up to the bottem of the oil pan...I just said to him, maybe you should get that water out of there