I forgot to mention that the ISOTEMP SPA series water heaters come with a 115 volt A/C power cord. I had to install a fiberglass outlet box. The original ATWOOD water heater was wired directly to the water heater. The wiring was long enough to mount on the inside of the galley cabinet, to the left of the new water heater.?
One thing to to remember is Marine wiring is stranded and tinned wire. Household wiring is solid copper - not to be used on boats per ABYC rules. There do not appear to be Marine grade outlets and residential grade outlets are made for stripped solid copper wire. Stranded wire does not wrap around outlet terminals and with vibration can loosen.
Good Old Boat magazine had an article recently about using crimped on ferrules to ameliorate this problem. The wire used by PSC is 12 gauge stranded wire. Using ferrules for 12 gauge took some effort to get a solid connection and did not wrap around the screw like solid copper wires does, so it was more of a compression fit on the outlet screw!
Another, perhaps better way may be to use a U shaped crimp wire connector with the locking tab: the industry name is forked flange crimping connector ( I believe). Reviewing commentary on ABYC rules, the ferrules and flanged fork terminals appear to be the approved methods.?
Daryl Clark