2003 Nautique 216 Electrical Issue

I recently picked up a new to me 2003 nautique 216 SE.  I actually like the fact that it has the simple dash and keyed ignition however, I may have the dreaded bad ground issues that seemed to plague me on my 91.  During the test drive of course everything was fine but after my first full weekend of running it (of course we put about 7 hours on it in 90 degree heat) I noticed some issues.  First when I turn the blower on the temp gauge and volt meter will jump a bit (temp up volts down) and when I turn it off it will sometimes go from charging at 12.5 volts to 13.5 or so.  This didn't really bother me however, every now and then it would drop under 12 volts and I could turn the blower on and off and it would jump back up to 13.  

The next issue I ran into was when I tried to fill the ballast tanks.  I pulled it out of the lift and flipped the switch to fill and everything went dead.  The boat turned off and I had no power to anything for probably 10 seconds.  It started right back up after that.  I decided not to risk it and filled the tanks by driving around.  I was able to empty them with no issues other than the turning on of various switches seems to make all of the gauges jump around a little bit. I am assuming there was some sort of power surcharge when I turned on the fill pumps that killed the power as a preventative measure.

I tried to do some research and it appears I may be able to just pull apart of the relay connections on the back of the engine and try and clean them.  Does anybody else have any other suggestions and an pictures or steps to where these relays are located? Or what else I should be looking for?  I looked under the dash and all of the connections there seem to be really clean with no corrosion.  I haven't tested the alternator but don't believe that is the issue with how the gauges jump around it seems like it is something in the wiring.  The boat is a 2003 but it only has 180 hours on it so maybe the sitting around has messed with some of the connections a bit.  Any help is appreciated.  Thanks.