I feel for ya, I acquired an old searay a few years ago, 95 model 220 and I don't like it so I have no desire to use it, but it was free. So at least the only thing I'm out is the parts I bought to get it going.
I have a 1/2 inch milwaukee probably 20 years old and it will turn a 5 inch hole saw with no problem other than when the saw binds up. All you can do is turn it loose. Hopefully the trigger lock is not in use.
At what point will you bolt it on and fair it into the boat's hull? seems like some of the additional layers will need to be extended into the boat. yes?
My old 2001 gmc has a message appear when it's down a quart but still have a dipstick. All this electronic stuff in a wet marine environment just seems crazy.