The sender could be bad or stuck inside. It could also have a short or bad wire. They are a pain to replace as the wires go through the transom assembly and plug in inside the bilge.
The sender just works on a pendulum type balancer inside that sends a signal to the guage.

Its basically already bypassed with the trailer/trim switch.

But is there a way to bypass it with the throttle switch, that'd make things a whole lot easier.

I've seen some posts about wiring it by the trim pump using a jumper , but I'm not exactly sure what to wire up???

I'm pretty sure it's a black 2 conductor wire that looks similar to a lamp cord. You can use a piggy back connector and jumper them together. (I've done this before, but it's been awhile. :p )

behind the motor there is 2 black zip wires comming through the transom for a total of 4 wires, 2 wires are for the trim sender and 2 are for the trim limit, the trim limit is the ones that let you operate from the throttle or from the trailer, the limit switches have 2 male bullet connectors on one side and 2 female on the other side, find those wires and jump them together and your trim switch should work if the sender is the problem. but at that point the system will nolonger know what positon the drive is in, so you will have to trim by feel.

is this what I should do?
http://www.offshoreonly.com/forums/a...1&d=1154390311

also here is pump......confused as to which wires to connect together.
http://www.offshoreonly.com/forums/a...1&d=1145981538

no to the first one, that is just a test to check the pump.
on the second one, the wires are there, but you can't see them, look behind the motor at the transom plate above the coupler, you will see 2 black exstension cord looking wires, they should be zip tied up so there out of way, find those wires and you will see the bullet connectors that i'm talking about.

No. This first one is showing how to test your solenoid. It's bypassing the solenoid and putting power directly to the trim motor.

OK so once I find the 2 black extension cord looking wires at the transom plate and the bullet connectors........then what do I do?

Sorry for the dumb questions....just want to make sure I get this right.

on one set of cords, there are a male and female bullet connector, those are for the trim sending unit gauge, on the other set of wires, there are 2 male connectors, those are for the trim limit, these are the 2 wires that you want to connect together, unplug them and the wires on the engine side need to be hooked together, that should make your trim switch on your controls work, it will bypass the trailer button and you will have full control of your trim and tilt from the shifter.

OK got it done, excellent directions.

Thanks very much for the help guys.