Diagnose my boat issue

[WBLskier]

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?

[oldjeep]

Sounds like a bad ground connection somewhere.

[Mick04]

+1 Oldjeep. How damp was it under your cover and under your motor box? Check for corrosion on any electrical connections (fuse box, computer, gauges, PP components, switch panel, kill switch, etc)

[Lieutenant Dan]

Sounds like a voltage issue. Check the battery and alternator

[Orlando76]

Check closely the battery terminals. Almost certain to be loose connections somewhere, most often the negative and the drop in oil pressure seems to verify that.

[Drago]

yup, i'd guess. battery/terminals. Tach only can be distributor

[LeonL]

Bad connections somewhere, most likely weak ground.

[Bdecker]

I once had an issue with a wire that had worn against the motor mounts and exhibited similar symptoms on my mastercraft. It's a shot in the dark for sure, but worth a look. This will be a super easy fix if that is your problem.

[Sethro]

On my 98 Echelon, I added a direct 10 gauge wire from the battery to my ground bar under the dash 15 years ago. I had some intermittent grounding issues before that.