Motor is '99 225EFI. My trim gauge has stopped working. In looking at the back of the gauge, all appears to be OK. My question is - how do I test the sensor on the outboard? It is mounted on the starboard side and has a black ground wire (that I have cleaned and cleck continuity to the neg. battery post) and a brown wire w/ white stripe.

Thanks,
Ron

Disconnect the trim sendor connect the ground wire and turn the sensor drive watch the gauge. Have seen Merc lose its connection through the main wiring harness via a connector. Trace the brown w/white stripe from sendor back to gauge.

Thanks Gary. I already unbolted the sensor, attached the ground directly to the battery and turned the dial on the back. The dash gauge does not move. Checked the voltage at the back of the gauge, brown/white has 8.4V. Brown/white connector on port side of motor is fine.

Ron

Only othe way to test the sendor is with an ohm meter while turning the center drive. Sounds to me like the sendor is bad.

Disconnect the brown wire wire with white stripe (comes from the trim sender into the engine cowling). Test "resistance" (with an Ohms Meter) between this wire and engine ground.

As you trim the engine up or down, you should see a "steady and relatively smooth" change in resistance (from approximately 20 ohms at "full up", to approximately 200 ohms at "full down").

Also check the continuity ground straps at the "port or left side" of the lower engine mounts (one exposed, the other is hidden under the mount cover). If either is damaged or broken, it will make the trim gauge work irratically (or not at all).

You can read more about it on this link: http://www.bbcboards.net/zerothread?id=487724

Thanks Keith! I will check both of those hopefully tonight.
Ron

if it is good at the sender , check for broken wire ( usually
at the spot where the wiring leaves the motor .(flex point)