temp guage troubleshooting
 

got a merc 150 2.0 with a temp guage, went out today and noticed it not working does anyone know a quick way to tell if it is the guage or the sending unit? what voltage if any should i be getting on the wire from the motor?

Disconnect the temp sending unit at the engine side and hook the wire going to the guage to ground. This should make the guage peg out. If it does then your sending unit is most likely bad, if it doesn't go to the guage and ground the wire coming from the sending unit. If the guage pegs out then you have a break in the wire, if it doesn't and you have power and ground at the guage, then your guage is bad. Also if you have the MERCURY factory style sending unit that is held in place with a rubber plug and a bracket, then the sender could have corrosion around it that is preventing it from working.

thanks ferm, i'll try this afternoon