Diagnose my boat issue

[WBL skier]

I have a 98 Malibu Echelon, Gen II Monsoon 325hp. I've had it 6 years and it has been bullet proof that entire time. Last weekend it started very rough and ran very rough. At first I thought I may have something in the fuel system. Then I noticed that all the electrical gauges were going crazy. When I turned the blower on the RPM's spiked. Perfect pass kept turning off and on. The speedometer was bouncing around despite holding a constant speed. The boat ran very rough and wouldn't start for a bit. I then thought it was an electrical issue affecting the EFI not something in the fuel system.

Then all of the issues disappeared by the end of the morning and it has run perfectly since. It did something similar once (but not as pronounced) earlier in the summer but then went away completely for 2 months. Strangely when I turn the blower off the oil pressure gauge drops by about 20. I wired perfect pass classic in myself about 2 years ago and it has worked well since. I did not do anything special with respect to running power to it (I know there are some on here who wire that in a special way). Does anyone have any thoughts?

[Michigan boarder]

Have you checked/cleaned the cannon plug?

[WBL skier]

Thanks.  Can anyone post a picture or description about where the Cannon Plug is and what I do to check/clean it?  I searched the forum a bit but didn't come up with a clear answer yet.  Thanks!

[Kmfish87]

Check, clean and tighten all ground wires starting at the battery terminals and engine block grounds

Edited October 6, 2016 by Kmfish87

[Michigan boarder]

52 minutes ago, WBL skier said:

Thanks.  Can anyone post a picture or description about where the Cannon Plug is and what I do to check/clean it?  I searched the forum a bit but didn't come up with a clear answer yet.  Thanks!

It is a round plug of wires located just above and behind the starter, about 2 inches in diameter (maybe a little less).  It should have a hose clamp holding the female end onto the male end.  If you were to pull your engine, you would disconnect this and it would free the entire engine electronics from the boat wiring harness.  Here's a pic, but it's kinda hard to see.

Not sure what the best product is to clean it, but I'm sure they have something at any auto parts store, some spray stuff that will clean it but leave no residue.