1985 17' conroy by glastron- voltage gage works only when boat is out of water....???

Hello,
First boat, so I'm learning my boat has a merc cruiser 140 w/ alpha one outdrive. When I run the boat w/ the muffs, on the trailer, volts read right on. Over 13 while running and 12 when motor not running w/ key on. Put the boat in the water, voltage gage malfunctions, drops to nothing, occasionally will rise between 9 and 11, never up to 12. Any ideas? Also I noticed the electrical wires going into the trim stop things(sorry, not sure of tech term) on the side of the outdrive, have about an inch of the wire insulation missing and bare wire exposed. They are in same shape on both sides of outdrive. Could this b my problem? Any advice/help would b greatly appreciated. Thank you.

Ken.

Re: 1985 17' conroy by glastron- voltage gage works only when boat is out of water...

Those wires on the sides go to the trim limiter switch and to the trim indicator guage. It is very common for them to become corroded. Unfortunately they are a real PITA to replace because the wires go through the transom behind the outdrive. They are almost definitely your problem and are shorting out your electrical system, which will eventually leave you stranded. What you can do, and what many people do, is bypass both of them. Inside the engine bay, you will see both sets of wires going to the transom. They will have bullet connectors to the harness. The two to the trim guage you can just disconnect and tape out of the way. The two to the trim limiter switch you need to disconnect and reconnect the ones from the harness to each other. The ones to the limiter switch may have male and female plugs, which would allow you to plug them to each other, or they may both be female so you'll have to make up a jumper wire. By jumping them you will bypass the safety which prevents you from raising the drive too high while in the water, so be careful with your trim-up. That switch normally allows you to raise your drive all the way up for trailering. If I remember correctly, the trim indicaotor wires are brown and the trim limiter wires are purple. I suggest you download manuals for your engine and drive to get the exact colors and for future reference. Hope this helps. Hy