There are thousands of A4s out there and very few related 'explosions'. In fact, as a sailboat auxillary a gas engine makes much more sense than a diesel. There is an elevated safety aspect wrt diesel vs gasoline, but with proper equipment and practices it's quite doable.
FWC A-4s are preferred, the RWC versions are going to be more prone to cooling issues and corrosion.
1984 Fast/Nicholson 345 "FastForward"
".. there is much you could do at sea with common sense.. and very little you could do without it.."
Capt G E Ericson (from "The Cruel Sea" by Nicholas Monsarrat)