Since the two wires are now properly fused, the issue is certainly less critical. As a matter of practice, one should NOT be constantly overloading a circuit and always depending on the fuse to prevent a fire. The fuse should act as device of last resort in the case of a very unusual circumstance.
Considering the following points:
1) The boat is not actively being used at the moment
2) An inverter CANNOT be run on the DC cigarette outlet
3) DC loads should be kept to a minimum, i.e. sequentially turned on
I would say that this recommendation can wait.