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Water temp gauge issue

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ankeneyou

New member
"Hi,

I just bought an 89 We

"Hi,

I just bought an 89 Wellcraft with 5.7 Merc and Aplpha 1 outdrive. I'm having an issue with the water temp gauge. The gauge was not working at all when I received it, the indicator was loose and was just pointing straight south.

I replaced the gauge and it read nothing. I replaced the temp sender and at first there was nothing but then it would go up to about 160, stay there for 5 seconds or so and then go back down to reading nothing. I had it out for about an hour last weekend and it did this continually the entire time I was on the lake. I was constantly checking the engine to see if it seemed to be running hot, and everything seemed ok (about 165 with temp gun). Anyone have any clue why the gauge will randomly work, then stop again after a few seconds?

I plan on replacing the wire from the temp sender to the gauge tonight or tomorrow as that’s the only other cause I can think of.

Thanks in advance."
 
"It's obviously an electri

"It's obviously an electrical issue. I would check the hot wire and ground wires to the gauge. If that does not work, then the wire from the sender is bad somewhere. Maybe check your 10 pin connector plug (where the boat harness plugs into the engine harness)for corrosion. Pin #3 (tan wire) is the one in question. Recheck the single wire connector at the sender.
Rod"
 
I'll replace the thermosta

I'll replace the thermostat and sender wire and also check all other connections.

I'll let you know what I find.

Thanks for your responses.
 
"Lee: when you check the temp

"Lee: when you check the temp sending unit, there are two nuts on it. Make sure the bottom nut is snug when you reattach the wire, lock washer and nut. You might consider changing the wire's connector at the sender since they are prone to corroding internally. If you find dark copper wire, scrape it to a bright shine before crimping on a new connector. Better yet, solder the cleaned wire to the connector and then shrink wrap it. Connectors on the engine tend to do as I explained and cause intermittent readings. T'Stat is also a good idea. Guy"
 
"Thanks for all your help guys

"Thanks for all your help guys, the gauge seems to be working fine now. I replaced the lead wire and t-stat.

One question though, the guy at west marine gave me a 143 degree t-stat. Is this correct? A 193 degree came out of it and I think that was the wrong one. I always thought that you want a gasoline engine to run at 175-180 though?"
 
"Older raw water cooled engine

"Older raw water cooled engines use 140 degree T'stats; newer ones use 160. FWC engines run 170 degree T'stats. It sounds like you got the right one alright. It sounds like someone had put a car T'stat in it, and that is the wrong thing to do.
Rod"
 
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