Merc 240 EFI Intermittent shut off

This season my 2000 challenger 2000 with Merc 240 efi shuts down at random times while underway. It may go a full day without shutdown or hours between shutdown. Yesterday in rough choppy water it would shutdown every minute or two. Each time it will start right back up and run fine until it stops again. This leads me to believe it is electrical related or a sensor going bad.

I read another similar post which was caused by a loose sparkplug boot but I pulled and reconnected each wire yesterday and the shutdowns continued. Today I am going to change the sparkplugs and look at the wireing for cracks and corrosion. Any other ideas?

Make sure to check all the connections from the ignition switch to the engine. I've read of a couple of instances of the ignition switch going bad and causing a similar type of problem. Also if you are thinking off a sensor, the crankshaft position sensor can cause a problem like this as well. Make sure it is secure and the connection looks good.

[attachment=658:General_Info.pdf] I'm sending you a pdf file, not sure if it took. If it did, go to page 9 and to the right of the spin on fuel filter (k) there will be a connection for your ecm. I have seen this problem before several times. the connection get corroded inside and some kind of erratic electrical problem follows. I have had your same problem before. The pin for the ground going to the fuel pump in the fuel vapor separator (E) on page 10 looses its connection. You will also loose the ground to the fuel primer (I) on page 10. Be careful checking it (the ground to the fuel pump in the fuel vapor separator (E) with a test light because the ecm supplies 12 volts to the ground when not in use. If that does not fix the problem try checking the black and yellow wire that runs throughout the harness. It could be grounding out somewhere. That black and yellow wire also comes from the lanyard switch and guardian module under the storage container in front of the steering wheel. If the black and yellow wire is grounded the motor will not run. That black and yellow wire runs to the CDM's (D) on page 9. Well thats enough to stars ,let us know if this helps, if not we can help you do some more trouble shooting.