300xs Shutdown while running

[jbutah]

2007 300xs SN:1E003178

I have a center console with twin 300 optimax and vessel view. Saturday, when running in at 35 mph, the starboard engine just shut off and the vessel view went dark. The port engine stayed running and acted normal, except with no vessel view I couldn't monitor anything. Fortunately we were not far from home and only had about a 45 minute idle the rest of the way. Once home I inspected all the obvious stuff. All connections are good, battery is good. I tried starting with the battery switch on combine and nothing. All the ignition and wiring harness connections are good. When I turn the key for the starboard engine nothing happens, no beep or anything. Port motor fires right up, but no vessel view. All other electrical items, pumps, electronics, stereo, etc. work fine. I have 4 group 31 batteries, one for each engine, and 2 for everything else. Any ideas? Thanks

[fishnfireman]

Just a blind stab-- did you check the motor mounted fuse ?

[Savage]

Check the Main Power Relay also.

[jbutah]

Thanks for the replies. Is the main power relay #5 in the electrical plate components diagram? Where is the fuse I should check?

[jbutah]

Thanks guys. It was one of the 20 amp fuses. Any idea why it would have blown?

[transdep1]

Check your coils, and coil harness. Look for a nicked wire

[low slung cruiser]

Check the main power lead that connects to the starter and the ground that connects to block... mine did vibrate loose once and same problem

[JOE54]

Check your coils, and coil harness. Look for a nicked wire

+1

[long shot]

Look at your coild and see if one appears to be oozing marshmallows out of a crack. Mine had a failed coil and it blew the same fuse. The white, fluffy stuff helps track it down.
Otherwise go and get a 15 or 20 amp circuit breaker that fits and try it while un plugging one coil at a time. One will trip it. I used a powrr probe to test mine and a friend's after a coil had failed on each of ours. Power probes have a 20 amp breaker so it was perfect.

[EuropeanAM]

+5, 6 and 7 on checking the Ignition Coils and Harness. Also inspect injector connectors for any signs of chafing wires.

That fuse blew for a reason, and if it blows again you could potentially cause PCM damage.

[jbutah]

So I have checked everything mentioned here. No apparent coil failures, engine ran fine last weekend. I actually just replaced the coil harness about 6 months ago with the newer style. There are no visible nicks or damage to any wires, and the main power relay and ground connection looked fine. What about the spark plug wires? externally they looked fine, but perhaps internally? They are original, 2007.

[EuropeanAM]

Although it would be unusual, I have seen at least 4 cases where incorrect Spark Plugs would blown fuses. Have not seen it occur with a plug wire, but that is conceivable if the wire were leaking at or near a harness lead on that fuse circuit.

[jbutah]

Forgot to update this. I got a new set of spark plug wires, and knock on wood, it has been running well.