Trim Sender works until it pops up and stays there

[dlogvine]

I bought a hull from the newer 2007 Baja Islander 202 boat. It came with the transom plate and bellows housing. I dropped my rebuilt engine and outdrive from my older 1993 Larson boat. The engine and outdrive are the same 5.0L mercruiser v8 with Alpha One gen 2 outdrive. Tested it on the lake and noticed that trim gage was going down way too early. It was sitting centered when the prop was almost out of the water and then when I moved it lower to the working position, trim gauge just moved all the way up and stayed there until I started lifting the outdrive. Should I just adjust the trim sending unit or it could be a bad one. The boat hull I bought was a rental one so it might have gone through a lot of abuse.
Thank you

 

[tpenfield]

Adjust the sender . . .

 

[dlogvine]

Adjust the sender . . .

I did try to adjust it, turned on the battery, dropped down the outdrive. Is it possible that it works only when the ignition key is on? Cause the arrow did not move at all. And I know it does when the engine is running. That is a very strange setup.