A 10 mile range over two hours ?????
I suspect you are making a mistake, friend.
I shudder to think of when you might be head to weather and you really must make progress against it.
With a Volvo MD17c, some 200 litres of diesel will take me 25 times as far.
Also, 48V with seawater-wet hands is going to quite an experience, hopefully brief.
12V is enough. Been there, done that.
A few points to consider.
If you've got a Volvo MD17c and a 200L tank, you're in a much bigger boat than me, probably something in the 36' range. Khaleesea is a Hunter 29.5, so blue water sailing would be a foolish mistake even with a diesel.
I sail in the Chesapeake bay. It's about 30 miles wide at the widest point, so you're never far from shore.
48V is the propulsion voltage, not the house voltage, which will stay at 12V.
I'm really curious to know under what circumstances I or anyone else would be doing electrical work on a live system with wet hands. That's so many bad decisions at once I'm having a hard time imagining it.
12v isn't enough voltage to push a 30' sailboat. Even if you max out a 4/0 wire at 12V, you get ~300A over a short distance. That's a whopping 5 mechanical HP.