3.0 L Mercruiser/alpha One-no Temp Gauge

[Skippy J]

I recently asked in this forum how to trouble shoot a temp gauge that was not working. I received really good info on how to ground temp gauge wire to sending unit case, which I did and the temp gauge went to the highest temp.

Next I purchased a new temp sending unit and installed it. Went to the lake this weekend hoping to be able to read my engine water temp. It did not work. Can someone please shed some light on what is the next step to take in solving this temp gauge problem??????

Thanks,

Skippy J

 

[Gary H NC]

Re: 3.0 L Mercruiser/alpha One-no Temp Gauge

Have you had the gauge out of the dash and cleaned the ground and sender wire connections?
You could also try running a temporary ground wire and sender wire to the gauge and see if it starts working.

 

[Rocky_Road]

Re: 3.0 L Mercruiser/alpha One-no Temp Gauge

I recently asked in this forum how to trouble shoot a temp gauge that was not working. I received really good info on how to ground temp gauge wire to sending unit case, which I did and the temp gauge went to the highest temp.

Next I purchased a new temp sending unit and installed it. Went to the lake this weekend hoping to be able to read my engine water temp. It did not work. Can someone please shed some light on what is the next step to take in solving this temp gauge problem??????

Thanks,

Skippy J

I hope that you didn't use any teflon tape to install the sending unit...the sending unit has to ground solidly to the block (thermostat housing), to work properly!

Tighten the thermostat housing bolts a tad...this is the ground connection to the block....

 

[Skippy J]

Re: 3.0 L Mercruiser/alpha One-no Temp Gauge

I briefly looked under the dash to inspect the back of the gauges. All my gauges seemed to be in one plastic box that does not seem very accessable.

But, I will look closer to check accessability. Did you say there is only a sender wire and a ground wire? There is no 12v wire at all??

Skippy J

Thank for the second reply, I did not use teflon tape, the factory sending unit did have some red coating on the upper threads, I think this was "locktite".

I wonder if I got the wrong sending unit? While purcashing the unit they pulled out a tray of units and I spotted one that was identical but the computer showed to use one that had a superceded part no. It it very similar but seemed a little shorter.

 

[Rocky_Road]

Re: 3.0 L Mercruiser/alpha One-no Temp Gauge

Is this what you have?

 

[Skippy J]

Re: 3.0 L Mercruiser/alpha One-no Temp Gauge

Thanks for reply..........do you mean engine or sending unit???

 

[ddecoursey]

Re: 3.0 L Mercruiser/alpha One-no Temp Gauge

I have the 5.7 260hp mercruiser (1983) Temp gauge just sits on"C"
I used the recommended method
took wire off the sending unit and grounded that to the block and the gauge goes all the way up to HOT every one tells me this verifies that your wiring tothe gauge and the gauge itself is in good working order.

So I go out and get the new sending unit.

It will only scew about halfway in..I tried everthing to get it to scew in farther but, that is as far as it wil go the acutal sensor( inch long finger at the bottom of the unit) is certainly down in the water flow.
The old one was only half way screwed in also I used no dope or teflon.
Attached the wire lead back onto the top of the unit and IT DOES NOT WORK the guage just sits down on the letter "C" and as a matter of fact after I shut the key off , the indictor will climb up to the first hash mark.... but soon as you turn the key to the run position it goes down off the 1st hash mark to the letter "c" this must be the bottom most position.




So if that is all you can test : Guage / wiring /and sending unit ...and that
1st test validates the guage and wiring to the guage....and you put a brand new sensor...... what the heck else is left to troubleshoot ??


summer will be gone and I will have not used this boat once at this rate