Two weekends ago I purchased a 1989 Wellcraft with Mercruisers 3.7 engine. All seemed well until this weekend when I installed a fish finder. While I was running down the lake I got a message on the fish finder that input voltage was too high . This caused me to pay attention to my in dash volt meter. Under acceleration and even at times while idling my volt meter shows that it is charging at 16 to 17 volts. Is my voltage regulator gone bad? This seems high to me. I wonder if dash gauge is even correct because fish finder is supposed to work from a 10 to 20 volts power source. Help! Any suggestions???