Temp Gauge
 

Well I fired the boat up after the long cold winter. Seems to be running fine except the temp gauge is not working. I let her run for a good 15-20 minutes so surely it got warm enough to register a little. Anyways, what can I check to see what the deal is?

Check the wire connections at the guage and on the sensor on the engine. Should be 2 sensors on the engine on the t-stat housing. One is for the guage, the other is for the overheat alarm. Not sure which is which.

What motor?

If it's EFI/MPI there is a sensor for the EFI system on the t-stat housing too.

the tan/blue wire is the audio warning
wire on a carbed engine, the audio warning
on a EFI is ran thru the 2 wire ECM coolant
sensor, the ECM controls audio warning.
The guage sender wires just push on to
the stud on the sender, check the connection
at the senders.
You can also check the connection at the
wire harness plug also.

the brown wire with the blue stripe is for the alarm and is on the starboard side on my boat.

its a 454 mag...carb'd. I checked the wires that are connecting at the tstat housing....just wiggled them a little. I'll pull the gauge pod and see if anything's loose behind it. Hmmmm....it worked last time I took it out, this is of course my first starting after winter, maybe just a dead gauge also?

Check to see if you have voltage to the back of that gauge, use a voltmeter or test light on the + terminal (with the key on).
Check for corrosion on all the terminals, especially at the engine.
Also disconnect and check the 10 pin harness plug at the engine.
Ground the temp sender wire connected to the sender on the intake manifold or thermostat housing (with the key on). It should peg the temp gauge.
If it does, replace the sender, if not replace the gauge or check for a bad wire/connection.
Gary

Maybe the thermostat is stuck open?

hmmm good point. I was just thinking myself...I wonder if the tstat is just stuck open. I replaced it the last time I took the boat out, stranger things have happened but maybe your right, it is stuck open. I'll check the gauge first.....if nothing gives there I'll pop open the housing and take a look there.