what I did
I have a 3HM35F although I don't think it matters what engine model. I bought the gauges from the local Yanmar dealer to make sure I had compatibility. There was a "tee" for the oil pressure sender, and a place to screw in the water temperature sender. I installed the gauges on the engine control panel, had to replace the on/off switch with a toggle switch and relocate the "buzzer" behind the panel. My on/off switch is now the battery selector switch, it has to be in the "off" position in order not to be able to start the engine from the cockpit.