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  #1   IP: 72.227.237.232
Old 10-07-2015, 10:14 PM
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CalebD CalebD is offline
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Spark plugs. Champion rn12mc4

dumb question of the day.

backstory.
My engine conked out on me the last time I was at my boat (ostensible Jaoquim prep); slowly came to a coughing halt after < 2 minutes of running. Had run reliably prior to this. I really didn't believe the cone of Jaoquim that the NWS/NHC was spouting so I left my sails on. Another symptom after the engine shut down was a heavy gas smell as fuel was leaking out of the carb air intake; drips but still.

today I resolved to drain the carb by the main passage plug catching the fuel in a clear glass jar. Fuel seemed quite clean. Then I went to change the spark plugs which didn't look so great on top but black on the bottom with some showing a sheen of moisture or fuel which might be consistent with her last choking, chortling shutdown with the carb dripping gas.

The first box of spare spark plugs I found on my boat were Champion rn12mc4's. RN12MC4'S !!! (***!)
Who can I blame for this?
I checked the body of the rn12 against the rjc12 that came out and the rn12 has a much deeper threaded entry into the combustion chamber.
I opted to use set of Autolite 437's I had which more closely match the rjc12's most of us use.
I believe that this Autolite plug is supposed to be a bit "hotter" than the rjc12's and I've used them before.
Once I started her up she started right up (she had been running quite well prior to this).

Here is where my ignorance starts to show.
Would the Champion RN12MC4 plugs even work in the Atomic 4? Would they be a bad choice of plug for the A4? What would happen if... ?

And finally, the question even I can't answer with certainty: How the hell did a boxed set of 4 Champion RN12MC4 plugs end up on my boat in the first place?

Are these the plugs for my 1998 Honda Accord perhaps, or did some Autozone clerk bifocal my request for RJC12 plugs and I did not notice?

It is good to have more than one set of sparks on board.
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Last edited by CalebD; 10-07-2015 at 10:22 PM.
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  #2   IP: 98.171.163.28
Old 10-08-2015, 01:29 AM
JOHN COOKSON JOHN COOKSON is offline
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Quote:
Originally Posted by CalebD View Post
dumb question of the day.
Once I started her up she started right up (she had been running quite well prior to this).
.
The suspense is killing me. Did the drippy carb and shutdowns go away?

TRUE GRIT
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  #3   IP: 137.200.0.106
Old 10-08-2015, 07:54 AM
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If the plugs will physically fit in the threads and not get hit by the pistons they would probably work more or less.
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  #4   IP: 71.118.13.238
Old 10-08-2015, 10:22 AM
Dave Neptune Dave Neptune is online now
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Caleb, just stick with the known workable plugs and don't fuss over the others just toss them!
The problem is not the plugs you have an over-rich issue! Check to be sure the choke is releasing ALL THE WAY first! If you feel the carb is OK look to doing a power time and if you still are fouling plugs you'll probably be dealing with the carb.

Dave Neptune
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  #5   IP: 72.227.237.232
Old 10-08-2015, 01:19 PM
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Quote:
Originally Posted by JOHN COOKSON View Post
The suspense is killing me. Did the drippy carb and shutdowns go away?

TRUE GRIT
Yes John. Engine ran great again.

And yes, I know I am probably running on the rich side (which explains the blackened plugs).

It is looking as if these plugs were for my Accord rather than the A4.
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