Mercury Pro Kicker 9.9 Spark Plug issue ?

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blueflood
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Mercury Pro Kicker 9.9 Spark Plug issue ?

Post by blueflood »

Hey everyone,
Removed plugs on outboard for winterizing.
What would cause one plug to be fouled ( the black sooty one which is in the upper cylinder) The other plug look fine (this is on the lower cylinder)

Engine is new and just broken in this summer.
It runs fine except maybe a tad high in idle. No hesitation, no sputtering, always turns over instantly.

Also, WOT is 5400rpm but sometimes in goes up to 6000. 5000-6000 is the operating range. It has not given up on the water, and runs smooth otherwise.

I usually cruise at 4000-4200 rpm and seldom WOT except for th break-in stated in manual. I followed the break-in procedure to a T with varied rpm for a certain amount of time. Approx 12 hours on it now. Also always use premium gas.

Help or suggestion ? What is going on ?

I found the gaps on both was .075 mm vs 1.00mm in the book. Replaced with new identical ones properly gapped.

So..If sooty carbon like fouling what does that indicate ?

Thanks !
Marc

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OrangeQuest
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Re: Mercury Pro Kicker 9.9 Spark Plug issue ?

Post by OrangeQuest »

Can you post a picture of both plugs. And I hope it was .75MM gap and not .075MM, that is a big difference. :)

Is it oily black or dry black and flaky? If it is new, take it to a dealer and let them diagnose or tell you it is normal.
"that it isn't just an ordinary sort of boat. Sometimes it's a Boat, and sometimes it's more of an Accident. It all depends." "Depends on what?" "On whether I'm on the top of it or underneath it."
A. A. Milne

blueflood
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Re: Mercury Pro Kicker 9.9 Spark Plug issue ?

Post by blueflood »

Hi Orange Quest,

Bottom one. Dry black, not flaky as I can tell. Kind of fused on except the flat on the last thread; there it flakes off. The other plug is fused on good at that spot. The fouling looks to be only on the insulator...the rest looks the same (both side electrodes are black - outdoors and angle shows it lighter) and the center electrode is darker on the dud.

The manual states 1mm for NKG DCPR6E on this O/B, the old ones are at 0.75mm 8O error :D on the wire gauge. It seems to be hotter on the lower thread area. I can't take it to the dealer but I was going to email them with this.
Image

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Last edited by blueflood on Mon Sep 19, 2022 9:39 pm, edited 2 times in total.

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OrangeQuest
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Re: Mercury Pro Kicker 9.9 Spark Plug issue ?

Post by OrangeQuest »

Could be from the smaller gap causing a colder firing of the plug, and/or you don't run it long enough to get the top cyl. warmed up completely. And/or, that cyl took longer for the rings to seat. Could be the motor is running a little to rich on that one cyl. Could be from however way you store the motor, a little oil creep into that cyl. and you just don't run it long enough or hard enough to burn the buildup off. Seen that a lot on std transmission vehicles that the customers shift to higher gears to soon and lug the motor down a bit and then bring it in due to poor MPGs. Rode test with them and they never get the engine past 1500 RPMs before shifting.

Like I stated, if it is still new, and under warranty, take the plugs to a dealer and ask them. The tech maybe able to tell you if it is a problem with the motor or operator, or it is normal. You have till next season to get them looked at.
"that it isn't just an ordinary sort of boat. Sometimes it's a Boat, and sometimes it's more of an Accident. It all depends." "Depends on what?" "On whether I'm on the top of it or underneath it."
A. A. Milne

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