Trim not working in Digital Tach Gauge

My first post. Sorry if this is not in the correct area.

My trim indicator (yamaha digital guage) always reads in the up position. When I lower the outboard the Tach trim meter jumps around a little but only goes down about 1/8 from full up bars.

I measured the Pink/Black pair from the tack back to the sender.
I get about .2 -.4 ohms - mostly the reading just jumps around its not smooth at all. Seems like I need a sender???? The sender cam mechanically moves freely and the plastic stop is intact. Unit is original on a 2003 z200txb (just 150 hrs)

Question are these the correct wires off the back of the gauge to be measuring? Would anyone suggest other methods to trouble shoot this or do I just replace the sender.

Are the wiring diagrams available online for these gauges??

[jb123]

follow the wires that go to the sender, there is a plastic cam that activates the sender and is most likely broken or cracked.

The sender cam rotates freely and the plastic cam stop is OK.

[jb123]

then check continuity of harness

Assuming I have the correct color pair (pink/black) which I believe I do as these are the colors coming off the sender (but I do not have a wiring diagram...). I get .2 to .4 ohms over the full range of trim motion. As I move the motor I get readings that jump around but stay within .2 to .4 ohms. I disconnected the tach input connector and measured back toward the sender throught the boat harness. So the harness has connectivity to the sender.

Do you know what the sender resistance range is? Seems like the sender is shorted inside, maybe full of salt. Is it worth trying to clean? Any posts on this?

When replacing the sender, do the wires attach to the sender or is there a terminal block inside the motor.

[boats.net]

The trim sender should measure 9-11 to 238.8-378.8 ohms between pink and black wire through the range.

Thanks I'll order a sender off your site.

Is there any preventative maintenace for this sender. I trailer, so I flush that area with a hose when I get home, should I be doing anything else.

Great resource, Thanks to all for help.

[CAPTJOE]

trim indicator inop

hi, on my engine (f225) the trim indicator cam has a "D" shaped hole and mates to the switch on a shaft with a "d" shaped end. the shaft had frozen in the switch and the hole in the plastic cam rounded out, giving the appearance of functioning properly, but in fact the cam was turning on the shaft, not actuating the switch. replacing the indicator switch finally solved the problem. just a shot.
capt joe