If you were otherwise happy with the Universal, I'd stick with it. Engine parts will be available inexpensively through Kubota, an option not available with Yanmar. If your present engine is FWC, have you considered simply rebuilding it? No installation complications and, again, parts/bearings/gaskets etc from Kubota should make that option quite palatable.
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)