Voltage fluctuations
 

Hey guy on my 98 330hp 454 Merc the voltage jumps around alot and its fluctuation is independent of engine rpm, one minute it will be at 8-10V and then it instantly jumps to 13 or 14V it does this more so when the boat just gets in the water but it will do it later on in the day just less frequently, does this sound like a voltage regulator problem? Both batteries are brand new optima's. The alternator is stock from what I can tell and has ~180 hrs on it. On these is in an internal regulator or external? Thanks for the help.

Re: Voltage fluctuations
 

Sounds like a bad connection or ground. Internal regulators usually either work or not, rarely will they fail intermittently.

Re: Voltage fluctuations
 

I had an intermittant diode that would heat up and cause strange effects, including high voltage, on the voltage regulator.
If the voltage doesn't go over the max 13.5V, then it could be a just loose wire.
Check the wiring connections. And if that doesn't fix it, take the alternator in and have them test it.
Gary