Mustang, I am going to go out on a limb here and suggest some additional activity. Fixing the leak is certainly a priority along with that unused ground wire. And based on your engine / sterndrive combination I assume you can trailer your boat home > i.e. get it out of the water and onto your driveway.
If yes, the suggested activity is to do a thorough wash down of the engine and the engine compartment / bilge. There are several reasons for this one of which is if you do have to use your bilge pump to pump overboard it will carry with it the oil contamination into the surrounding water. Better to wash all that down and out of the drain plug where it can be better managed. Also, a clean engine / bilge will be more telling of any issues like an oil or hyd leak. And just as important, at least to me, is that its much nicer to work on a clean motor.
A number of methods exist to do this, and we all have our preferences. The key is to be careful about it and protect the needed components. If you have an air compressor, all the better to dry off components. An alternative is to talk to your local car detailer and ask them if they would take this on.
If DIY, it will take an afternoon and cost about $50 in engine cleaner and other things like brushes that you will toss once done. If go the detailing route perhaps $200 to $300. Either way I suspect you will be happy you did.
Thanks for listening.
