a beautiful boat should sail forever.
This is a 1/2" fitting on front of the thermostat allowing both a "sender" for the gauge (on right) and a "switch" for the alarm. Note the two wires on the sender, one for the upper helm and one for the lower helm. Also note that the switch is 3/8" pipe threads, so a 1/2" sleeve had to be added.
This is a good time to remind you that these fittings must make good contact with the engine block to provide the ground that completes the circuit, so use Teflon tape sparingly. You can check to see if the circuit is grounded, with a volt meter connected to any 12 volt source in the system.
BE SURE TO LABEL ALL YOUR WIRES!!!!!!!!!