Are you running 1 or 2 batteries . If 2 what type of switch. If 2 batteries both (-) leads need to have a ground wire, 2 gauge, that is grounded directly to the block.. Not just jumping one neg on one battery to the other neg of the other battery with a short wire. Next trace the wire to the block where it is grounded . Undo the bolt or nut and clean up well with WD40 and wire brush and re-install . Third locate the ground wire under the dash and trace it back to the battery or where ever it goes. Replace it with 6-8 gauge wire. Fourth if there is zip tie smashing the wiring harness connector, cut it loose. Also a good idea to put some Di-electric grease on the wiring harness pins.. One of these things or a combination of these things MIGHT be causing your problem. Good news is doing all of these things cost less than 100.00 and prob need to be done to any boat over 5 yrs old anyway. Might also be worth having the ecm sent off to have tested. If you want I can get you name of the place to send it.

Good Luck

Chris

also try to spread the male pins at the main harness

I know the boat is a 2000 the ecm says 03 but the harness says
2000. I bypassed the lanyard. Usually when it shuts off it will
restart immediately. I did have it not start on the trailer and after
going through everything it started up to no rhyme or reason.

I will go over everything you said and let you know. Thanks for the
help. Would a bad ECM make all the gauged go flat on shut off? Sure sounds like the ignition switch or grounding out somewhere to me.

Thanks

I had the same problem with my 502 EFI. The answer was to pull that big round main electrical harness plug apart and use something like an ice pick or nail and stick in in the center of the male end of those prongs. they will spread out and make a tighter connection when plugged back in. And make sure those are clean also.

I spent a whole summer of running down the lake and out of nowhere it would just shut off ,,, guages and everything.

I would stop and restart it and it would do it again somewhere later on. It was frustrating to no end I tell you.

Be careful when you pull that plug out ,,,sometimes those prongs will rip out. Had to hardwire a couple of them because of that.

Post your engine serial # also did you scan this motor for codes. Also would agree to stick a pick in between the male pins from the main engine harness to spread them out making better contact. 4 things come to mind - connections, resistance, corrosion, heat somewhere in this system, one of these or more is the cause. I know thats a broad range statement.

Also check the main power relay and the connections. This is also called MPR. the leads for that are red/ppl, red/blk, pnk/dk grn this lead is also main power lead to the ECM. Its always tough to fix these kind of problems especially without your hands and eyes on them. Good luck.

Thanks to everyone for all the good help! I will try step by step
and eliminate one by one.

Thanks

So what was the diagnosis?
 

Just wondering what was the cause of the problem?

THX

I have had that problem twice with my port motor. Usually after a hard landing (thanks Jeff) but what I found was the main 50amp breaker on that motor would trip.exact same symtom only I had to reset the breaker to fix it. Just a thought maybe a weak breaker,bad connection?

Good call - that happened to me last season

Well I finally fixed it, I replaced the engine wiring harness, have ran it for 20 hours or so and works great.

Thanks