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| Just changed the spark plugs in my Suzuki 90 hp tiller. It is a 2003 4 stroke, fuel injected motor. Runs great, starts easily. But, I noticed as I have a couple times before, the bottom plug of the 4 plugs was more fouled than the others. I vaguely remember the dealer service guy saying something about that on my 2008 Mercury 90 hp on my pontoon when I took it in for a minor service issue under warranty.
Any insight on this? Again, runs good but just wondering about this issue. | |
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Location: Athens, Ohio | As with any motor, "it's either fuel or fire."
If the coil and spark check out equal with the others, perhaps the valve is not allowing spent fuel to exit properly? m | |
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Posts: 3480
Location: Elk River, Minnesota | Hiya,
The only thing I can think of is the plug maybe wasn't gapped the same as the others causing it to burn less efficiently?
I know some engines like the Evinrude E-tec engines need their plugs indexed correctly to run efficiently. I believe they are set to have the open side of the plug's electrode facing the injector port for the cylinder.
I've not heard of needing that on any 4-stroke engine, so it's a shot in the dark as to whether this would be the case or not..
Being a fuel injected engine, I would say it definitely is not a fuel related unless the injector was a touch dirty. If the engine is running well, I doubt it would be that issue...
Steve | |
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| Thanks for the replies. As I said, runs well, starts immediately, idles smoothly. Just seems odd the for the second time in a row the bottom plug was "dirtier" than the other three. I had the motor checked by a dealer last year and they said everything was running fine. I had taken it in to get the impeller replaced, while they cleaned the carb on the kicker and had asked they just give it a check. I thought as long as I was hauling the boat to the dealer, have both motors checked out. (VMS had diagnosed the problem with the kicker as dirty carb and that was it. Runs great now.) | |
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Posts: 320
| If it starts great, runs and idles smooth, I wouldn’t worry about it. Just get out there and fish!!! Good luck!!! | |
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Posts: 1087
Location: Hayward, WI | Are you letting the motor sit tucked in? Oil can settle in the cylinder if you are and can foul the plugs a little. When the motor is sitting, not running, have it tilted just out from vertical when sitting. | |
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| kjgmh - 4/25/2020 9:16 AM
Are you letting the motor sit tucked in? Oil can settle in the cylinder if you are and can foul the plugs a little. When the motor is sitting, not running, have it tilted just out from vertical when sitting.
This could be what happened. It spends the summer on the lift and I don't typically tilt the motor because there is no need, but will try that this summer. And that is what it seems like I am seeing, a little oil on the plug. Thanks, can't hurt and while not a big issue would like to see what the cause is. | |
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Spark Plug issue