Water Temp Sensor & Temp gauge problem

[HPLou]

MCM. 4.3LX 205 HP OC534197 with Alpha One R/MR OF162055
I have twin engine Merc 4.3lx. The Starb Engine Temp Gauge does not move at all. I have jump the Starb Temp Gauge with the Port side Engine to test
if the gauge would move. It did. So I confirm the Star Temp Engine Gauge does work OK.
So I decided to replace the Water Engine Temp Sensor of the Star Engine with a new one.
I bought Sierra 18-5897 (located on the Port side of the Thermostat Housing) and installed.
The boat is in the water so I went for a test ride and the Star Engine Temp Gauge worked perfect for about 15-20 minutes and very slowly
died to not functionning any more.
This is a mysterious problem and I would like some help please.

 

[alldodge]

Sounds like you have a bad wire or wire connection. Check close at the connections or run a temporary wire from gauge to sender and see if it continues to work. If it does not continue to work then it might be the gauge. I say maybe the gauge (if wire doesn't work) because the gauge did work when swapped, but thinking it may not have been used the 15-20 minutes like when sender was replaced.

 

[Bondo]

This is a mysterious problem and I would like some help please.

Ayuh,..... Check the cannon plug that connects the motor to the boat,...

Also the Grounds to the block,....

 

[HPLou]

Thank you for your replies.
I will run a tire from gauge to sender and test
I will check the cannon plug & ground to the block.
This will be done today, latest tomorrow and I'll get back.
I Appreciate your help.