Johnson 200 Venom 1995 trim gauge problem

[Diesel Doctor]

Trim gauge has never worked. Bought boat used. Needle on gauge stays to the far left. I have moved the sending unit with the key on and it does nothing.
What is the most common issue with this type problem. Wiring, gauge, sender. Also best way to troubleshoot.
Thanks for any advise
Eric

[boats.net]

Could be any of those issues. If you manually move the sender and nothing, then try grounding the guage, this should peg the needle. If the needle then moves, chances are sender then wiring.