There is no standard temp or oil pressure gauge with honda. Most likely, they are left over from a previous motor (most likely a Mercury) that was installed and are still wired in.
In any case, if those other gauges at least move when the key switch comes on them the rest should be fairly straightforward.
See how the the colored leads loop from gauge to gauge. Hopefully, they left the old harness connected. If the Mercury set up is still there, there should be a purple lead (switched positive) that loops from gauge to gauge. There most likely is a similar wire looping between the tach and the trim gauge. It might be purple or whatever color they chose. The wire will be connected to the "I" terminal, positive or Battery (different manufacturers different designations for the battery post). Follow that looping and see where it leaves those two gauges. It probably goes to the switch that you mentioned.
Take that lead off of the switch or where ever it is going and connect it to one of the terminals with the purple lead of the gauges that do work.
That probably will do it....I am assuming that the grounds (black leads) are all connected together somewhere.
Not seeing it firsthand, it is hard to tell what you have. Just connect it with a temporary jumper, just in case my assumption is not correct. Then you can pull it off quickly during the test.
Bottom line, the switched voltage comes from the engine on a black/yellow lead. It then can be looped from gauge to gauge. Black is ground
That last two sentences may be all you were looking for.
Mike
Mike
Mike
