Boat needs to be out of the water, trailer is best. My drive stayed on for the gut replacement. But, You need to make some decisions. How old is the Gimbal, Shift, Exhaust bellows and water pipe. Up 0 to 5 yrs ok, maybe 7 yrs. to 8 yrs. maybe ok, older a change is necessary, check for softness, That is another Thread. If its brittle you should change and pull the drive. Do all the work together, along with new trim limit and sender wires etc. Or plan to do in the winter. You will take on water and possibly sink if any of the bellows crack, no way to stop water except continuous pump out. Ok, To get you thru the season. I went and bought a new Sierra trim sender/limit kit. Pay attention to how the parts sit inside the units, take pictures. Not alot of youtube videos on this or how to calibrate. What i did was, turn the wheel to the right, remove 4 small cover screws and take sender cap off, remove 2 screws hold sender to the drive. now the sender housing is hanging from the boat. There is a screw holding the contact in the sender to the wire, remove the screw. replace the parts from the new kit. be careful with the contacts as the tiny thin arms break easily. replace the contact to the wire (clean the wires and bare copper) and rebuild. after you have rebuilt one side, turn the wheel and do the other side. If you have a Selco manual it will tell you how far up to raise the drive to calibrate the limit, (you may need somebody at the wheel while calibrating, raise and lowering. There is also a baseline start point, my bravo iii is something like 20 3/4" bolt to bolt on the trim cylinder. Selco will explain. Unless you have done this many times you will need to go back and forth adjusting the trim and the gauge. also know that there is a full trailer setting. You don't want to include that height in the calibration, you could damage the drive shaft. If after you replace the guts of the sender/limit and you don't see any effects on the gauge even after you have tried adjusting. Then your wires might be gone or you have a bad gauge. inspect the wires. doubtful on the gauge. let us know how you did.