300X problems

[Phillip A. Griffith]

I have a Cougar 23MTR tunnel with (2) 2001 300X engines. The right engine has been shutting down like hitting the kill switch. The kill switch is common to both engines so its not at farult. It occurs at any rpm and usually happens after heat soaking for few minutes. Usually happens after 15 minutes or so. I've been swapping electrical parts from engine/engine. As a matter of fact I've swapped every electrical part on the right engine. I've run a DDT on it and no problem is indicated. I've checked fuel pressure on the fly...it remains at 40psi. I put in a new 1000a/h battery and it seemed to improve for two 1 hour trips, now it's back to the same thing. I tried to check spark on the fly but it's very difficult. I even crossed fuel supply lines to eliminate that. I swapped all the coils and ignition units so I feel that eliminates them. This is gettiing ridiculous...it's been a problem since it had 25hrs on it and Mercury never stood behind the problem. Any ideas would be appreciated from you guys since this problem has been going on for 3 years! :mad:

[WILDMAN]

I've had two or three shut off for no apparent reason, only to start up again. It's almost always the big plug where the harness plugs into the motor. Unplug it and spread out the pins. Clean it real good, and try it again.

[Phillip A. Griffith]

Thanks for the tip, I'll try it.

[THE HOGG]

I Had Some Problems With My 3 Litre And Finally Discovered That It Was The Plug On The Top Ecu. It Faces Up And Water Had Seeped In And Corroded All The Pins On The Ecu And The Plug. I Cleaned It Up And Wd40'd The Piss Out Of It. No More Problems So Far.

[Motion35]

There are two diode's in the Mercury kill switch 2-to-1 splitter. Mercury sell's the diode kit as a separate part number. It plugs in just behind the kill switch.

[lugger]

i had the sam problen on my 60hp undr the cowel ehre the harnes connects , spred the pins . all good . i heard merc chaned ther plug to stop that , i thought it was kill switch , mine would not start , then i get home to diagnoe it was ok . let sit over knight wont start
i wiggle tested all wiring untill started , . try wiggle that connector when it does it again good luck