Running boat with only 5 of the 6 spark plugs connected

[Ozweego]

So as I continue to troubleshoot my lack of performance and troublesome cold start issues I discovered today that one of the six spark plugs was not connected or plugged in.

The black plug wire simply was not put on the spark plug. I had a boat shop do the service for me and only discovered it now. I have been running the boat for approximately a month like this. This morning I plugged it in and took it out for a run. I still have problems on cold start as it takes me 3 to 4 times to start it up also my performance did not go about 4,900 RPM.

My question is now with the spark plug that wasn't plugged in foul up? As I can only imagine running five cylinders as opposed to six would decrease engine performance I was hoping I would see a noticeable boost when I put the 6th plug back in.

Any advice appreciated.

 

[POPPS]

What motor is this?

 

[Ozweego]

Mercury Optimax 250 with M2.

 

[POPPS]

Apologies,,,am 2 stroke sesdoo,,,pop over to the merc threads,,,i am sure you will find helpful threads.

 

[ripcuda]

What color/condition is the disconnected spark plug? I would think the plug is fine. I had an issue on my engine where 2 plugs stopped sparking... and the plug looked new... and works fine now that I fixed my spark issue. A prolonged non-firing cylinder... I wouldn't think it would cause any issues beyond possible issues to the CDM (aka coil) for that non connected spark plug. I've heard you should always ground the spark plug wire when disconnected on a coil that will be sparking. There might be a possibility that your CDM for plug got damaged due to not being grounded while sparking for so long. Use an inductive timing light on that cylinder plug wire (and check the others too) while running and ensure you are getting spark on all cylinders.