| Fredo, an aftermarket temp guage will come with a "paste on" temp
sensor that is secured to a specific location on the motor's head. You
may have to scrape some paint away at the location of the installation.
You route the lead from the sensor is routed to the dash panel, and
connect to the gauge. The guage should have a positive (blade) and
negative (stud/nut) for power, and probably an extra terminal blade for
the lighting control circuit (from the nav/anchor switch or an adjacent
gauge). I believe some of the newer motors with electronics built in have a
temp sensor as part of the mechanicals, but I don't think that
describes your 90 Merc. I installed a trim guage on an OMC powered boat last year, and if...a
big if...I recall correctly, the gauge readout is based on varying
resistance (ohms) through the lead wires. You can take a volt-ohmeter
and measure the resistance with the motor in different positions across
the gauge terminals. If the resistance reading doesn't vary, it's
something at the motor, probably the sender, or faulty lead wiring. If
you get variable readings, then the gauge is stuck/malfunctioning. |
rbstern
Aug 14
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