Tilt/Trim Guage, Sending unit

[TFStelten]

My OMC king Cobra trim guage is jumping all over the place, all the time. This Chris*Craft is now 14 years old. Do these sending units simply go bad after awhile, or should I concentrate on checking wiring problems? Do you know of anyplace to get a good used one?<br /><br />Thanks in advance to anyone answering this note.<br /><br />-Tom

 

[Elk Chaser]

Re: Tilt/Trim Guage, Sending unit

Check the obvious first, the wiring and connections. I would say that the sending units can corrode over time internally and may cause problems but it is the least likely problem. <br /><br />My sending unit mounting holes had corrosion and the screws would not stay tight causing exactly what you described. I was not able to fix it fast enough and it fell off and was crushed by the outdrive while turning. So for now I don't have a sending unit.

 

[Boatin Bob]

Re: Tilt/Trim Guage, Sending unit

I would say that if you managed to go 14 yrs on the original sender that you are very lucky, eventually the seal on the arm wears through and water gets inside and corrodes the rheostat type device which gives you flaky readings because the resistance is always changing. There is no such thing as a good used one, you will either have to live with it or replace with new. If you can find the double black wire that comes through the transom mount behind the engine, follow that to the connector and pull it apart, now use an ohm meter and check the resistance, I don't remember the exact numbers but it's something like around 200 ohms down and around 10 ohms all the way up. If the boat is out of the water then you can manually move it up and down. If you are outside of these readings or the needle goes all over then the sender is bad.