I concur with Cam..
Don't do it in the water except in dire emergency. Some one at the dock told me that I didn't need to haul out to put my transducer in. LIAR I removed the plug with the transducer ready to go in place ( imagine a 2" fire hose going off in your face) I gave that transducer CPR for the next 30 minutes or so hoping the plastic would not give way and I wouldn't cross thread the damn plastic nut and the love of my life sticks her head into the comanionway and belts out "why did you have to wait till we were ready to leave to do that" bless her heart. Never will I attempt that again except in an emergency. This happened on a Sunday and I had to get back to work, Monday was a Holiday for the normal folks, I had to work and all I could think about was holding pressure on this stupid leak I created till Tuesday. Now more intelligent cruisers will attest to the fact that you can pull this maneuver off with a toilet plunger. To that I say hind sight is always 20/20