1992 175 hp Merc Voltage problems

I have a 1992 175 hp Mercury EFI mounted on a 19 ft Sea Ray Ski Ray. Typically the voltage meter sits at around 14 volts. However, when going through rough water the voltage will go up to 18 volts. Trimming the motor up or down sometimes will take it down to 14 volts and keep it there. Sometimes bounce on the waves kicks it back to 14 volts. When using lights, and the voltage jumps up the lights also gets brighter. I also notice the Tach and temp go up slightly. I suspect a short or the voltage regulator but dont know where to start looking.

Re: 1992 175 hp Merc Voltage problems

It would sound like a failing voltage regulator. When you use the power trim it puts a drain on the battery and hence the alternator has somewhere to put the charge and the voltage drops until the battery fully charges again. The more external load you put on the battery eg Lights, pumps,electronics,etc then the charging voltage should drop as the charging circuit has more to do to keep the battery charge up. Have your battery checked and if that is OK then I would think a voltage reg is down. I am not sure about the EFI version but the carbed V6 motors have 2 voltage regulators. Hopefully only one is gone. It is something that should be investigated and fixed before it fries some of your electronic equipment.

Re: 1992 175 hp Merc Voltage problems

I would suspect a high resistance or loose connection, especially when you say bouncing causes state changes.