If the motor runs but the gauges do not have any power, then power is getting to the key switch.
There is no "fusible link" that I know of.
If the gauge wiring harness is from Honda, then there is a 7.5 amp fuse in the harness on the black/yellow lead.
Since there is power to the key switch, then when the key switch is turned to on, there should be 12v applied to the black/yellow lead to the gauges. If it is a repower, using older existing gauges, then the black/yellow lead might be connected to a purple lead, going to the gauges.
You just have to trace the voltage from the switch. Could just be a bad connection.
Also...don't forget to check the ground wire going to the gauges.....in case of a broken lead or connection.
You did not say how old the motor is but a wiring diagram can be found in the back of the owner's manual. See page 104
http://cdn.powerequipment.honda.com/marine/pdf/manuals/31ZW4607.pdf
Mike