I have a QO square d panel with 8 breakers.
factory install, but the boat is from 1970!
I recently went thru the whole system and repainted the metal box breaker box. Everything was in good shape. Their is an issue and that is the wire clamping, the wires when multistrand need to have the strands secured by a clamp action which does not cut the wires, my box is fine in that regard.
I suppose you could put a crimp on the wire end and secure that in a box using a screw clamp that simply bears down on the wire. Sometimes I have soldered the wire ends. I soldered all the wire ends for the outlets, then wrapped them round the screw heads. I used 12 gauge multistrand wire same as an extension cord. I have not noticed any wire troubles and few of my wires are marine tinned.
Much of the wire I recently changed was solid romex and that was in good shape regardless of what people will say, it was in good shape in a 40 year old installation
Maybe your FG boats shake, sputter, vibrate but mine does not seem to vibrate or work
harden 40 year old romex anywhere.