3.0L Mercruiser/alpha1- Temp gauge not working

[Skippy J]

Recently purchased a 1987' 18ft Wellcraft open bow classic. First time on water last weekend. While looking at all the gauges on dash, I noticed everything worked except the water temp gauge.

Please assist with remedy and where to start looking for problem.

Thanks,

Skippy J

 

[Bt Doctur]

Re: 3.0L Mercruiser/alpha1- Temp gauge not working

At the therm housing locate the sender and using a jumper from the wire to the sender body, with key on, gauge should go all the way over.
Yes: wiring good, reolace sender
No: wiring bad

 

[Skippy J]

Re: 3.0L Mercruiser/alpha1- Temp gauge not working

Thank you for your response.

Are you saying to jumper a wire from the wire that is attached to the sending unit to the sending unit body? Is this grounding the wire? If so, by grounding wire, this will make gauge go to highest temp? Will this indicated gauge is good and sending unit is bad?

Skippy J

 

[rbh]

Re: 3.0L Mercruiser/alpha1- Temp gauge not working

yes if you throw a dead ground on the wire that goes to the sending unit the needle on the gauge should peg over to the high side of the gauge as the gauge works on resistance. If it does not peg all the way over, pull gauge and make sure the wires are attached and they have good contact if nothing trace back to sender. check the grounds and remember the key must be on.DC power must have clean and tight contacts, positive leads as well as grounds or it will not work
rob

 

[180shabah]

Re: 3.0L Mercruiser/alpha1- Temp gauge not working

If you download the service manual from the adults only section, you can see a wiring diagram.

Also, you will have the "book" the next time you need it. Like winterizing

 

[Fishermark]

Re: 3.0L Mercruiser/alpha1- Temp gauge not working

If you find that it is a wiring issue, a common place for there to be a connection problem is at the big wiring plug located on the engine somewhere - where the boat wiring harness plugs into the round plug. Just a place to look if you find the problem lies in your wiring.

 

[Skippy J]

Re: 3.0L Mercruiser/alpha1- Temp gauge not working

Ok, I grounded the wire that was attached to the water temp sending unit and indeed the temp gauge on the dash went to the highest temperature. I picked up a new sending unit at a local boat dealership, $32.00. I noticed online I could have oredered the same part for $19.00.

Thanks for all your tips and advise, hopefully I will be able to read my engine temp this weekend at the lake.

Skippy J