Inside boat back at transom.
Oh, I hope you have access. Mine was real difficult to get to with the 4.3L in there and I have the large engine bay with the big sun deck covering it, not just a dog house.
Theres a through the transom gear lube bulkhead fitting going through the transom. That's where that hose connects. Most of those fittings are plastic, a few are brass. Look for a stem sticking out. Maybe your hose just broke and all you need to do is reconnect it.
I dont know how your's got disconnected. I hope the fitting didn't break. Is there anything still connected to the end of that hose? I hope not.
It might not hurt, but I wouldn't run it with it open like that.
There are different bulkhead fittings depending on your setup.
I broke mine off from the outside while doing a bellows job. I had no idea that thing was plastic or I would have been more careful with it.
It gets pushed in from the outside and held in with an "E" clip on the inside. At least that's how mine is, your's could be different. I could barely reach it behind the engine with one hand. I had to use my phone to see it.
So, look directly behind the engine on the transom. That stud should be sticking out.