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1987 Johnson 90hp clean spark plug

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Joycejh11

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After running my engine for several hours I’m still having problems with 1 spark plug. The lower port cylinder’s spark plug is incredibly clean, even the threads. I’ve replaced the plug, coil, wire, and confirmed I have good spark. Any thoughts would be appreciated 218BBB5B-BFAB-4C2C-A461-C41018821594.jpegD2A4D3DE-A009-45A6-8D0D-4FE6958A9D07.jpegDF4DE3DE-6F73-432D-9308-38FA1309F2F3.jpeg
 
Reasons.----No fuel ,way too much fuel, no compression , no crankcase compression or weak spark.------Do a compression test first.----Then see if spark will jump a gap of 3/8" or more.----What fuel pump is on this motor ?
 
racerone said:
Reasons.----No fuel ,way too much fuel, no compression , no crankcase compression or weak spark.------Do a compression test first.----Then see if spark will jump a gap of 3/8" or more.----What fuel pump is on this motor ?
Click to expand...

Compression test is 112psi in that cylinder. All the rest are between 112-120. Bought a spark tester and all of them jump well beyond a 3/8” gap. Doesn’t seem like over fueling is an issue nor does under fueling. Spark plug is clearly wet. It has the older non VRO style fuel pump. All other cylinders are running perfectly as can be seen in the photo. Main thought I’m coming to is potentially water getting into the cylinder... but with the compression being adequate I’m hesitant to pull the head.
 
Water getting into the cylinder was my first thought, but I decided to go the simpler route until proven otherwise. Is it "wet" with fuel or is it wet with water?
 
fdrgator said:
Water getting into the cylinder was my first thought, but I decided to go the simpler route until proven otherwise. Is it "wet" with fuel or is it wet with water?
Click to expand...

I can’t quite tell, it looks more like a milky gas mix. So a combo of the two. Do you know which gaskets would allow water to enter the cylinder? I’m assuming head gasket and exhaust gasket.
 
Milky? That's water. It can destroy the engine if not attended to.​ Likely leaks are head gasket or exhaust gaskets.
 
I know this thread hasn't been replied to in some time. I just wanted to come on here and post the solution to my problem in case anyone else is experiencing the same thing...

I had replaced the plugs and wires I don't know how many times trying to get this cylinder to fire. One day I was out on the water and my battery died, so I had to pull start the motor. Turns out, while the cover is off, it would run on all 4 cylinders, I had never run the boat on the water without the cover on until that day. I went from struggling to getting up on a plane to flying out of the water. Anyways, the moment that engine cover went back on it would ground that spark plug wire to the case, the inside lever mechanism was just barely cutting through my plug wire and taking away all spark to that cylinder.

Hope this helps someone.
 
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