Standard wiring diagram

First step is a volt meter and start checking power and fuses

Like Dan said, meter and time.... the colors for the wiring are mostly standard and I doubt you will find the scheme for that mistress, I could not find one with my 85, start at the switch and see if you have power, if not go backwards to panel as nothing is labled, if you have power to switch check wiring out, and grounds... odd to lose them all so I will say most likely power to switch.

Prob rodent eat the wires - man this is so common in my area. The rodents actually think the wire insulation is food because the insulation can be made and or has a soy base product in it.

Every darn spring someones boat has chewed up wires for whatever.

Not sure what problems he`s trying to solve when the boat hasn`t even been delivered.