Fouled plugs?

[PensacolaJason]

We were out yesterday and moving quite well when all of a sudden after pushing it almost full throttle for a few minutes, which we rarely do, the motor stuttered and then stalled. We tried starting again immediately and it would crank but not turn over. After a few more minutes it turned over but sounded pretty bad, like it was missing, so we limped a few hundred yards back to the dock barely above idle. It was smoking more than normal and I could smell a little gas. I pulled the plugs today and they looked covered in oil. Also, they were NGK's and this motor suggests Champion plugs. Might also add that the oil pump has been disabled so I pre-mix now.

My question is do you guys think fouled plugs would cause this and do these plugs look like they might be the culprit? Are their any other tests or troubleshooting I should do?

The motor is a 1987 Evinrude 120 hp E120TXCUR

 

[racerone]

Report the results of a compression test.----And does spark jump a gap of 7/16" on all 4 leads , yes or no ?

 

[Vic.S]

It is not going to run with plugs in that state

The currently recommended plugs are Champion QL78YC gapped at 0.030" ( although originally QL77JC4 I beleive)

You dont say what NGK plugs are fitted. There's no exact equivalent The nearest is BPZ7HS-10. I'd change them to the recommended Champions.

If you have or can beg, borrow or steal a compression tester do a compression test.

Also check that you have 4 good blue sparks that will jump at least 3/8"

Are you sure your oil mix is correct? ... 50:1 ?

 

[emdsapmgr]

Did you hear an overheat warning horn? Possible the engine suffered an overheat lockup at high rpm's. When that happens, the engine rotating assembly locks up solid. Once the engine cools, it can be cranked again. Often when you suffer this failure, other damage is done to the powerhead. Do a compression check. Not unusual to see oil on the plugs-esp if the engine has been idling. It runs rich at lower rpm's-that's normal.

 

[F_R]

In my humble opinion, those plugs are not fouled. Besides, it would be nearly impossible for all four to foul at the same time and stop the motor. However, they may be a symptom of something else that has happened. I agree, check the basics, especially spark and compression. And yes, the fuel. For all we know, there may be a puddle of water in the gas tank, or the pump may be sucking air from a leak.

 

[PensacolaJason]

No Title

Update: I went back and warmed the motor up and ran the test again with all spark plugs removed and updated the results below. One cylinder is measuring half of what the others are. Also, the motor smokes quite a bit more than normal.

Here are the results of my compression test on all four cylinders:

Top Left: 120
Bottom Left: 120

Top right: 60
Bottom Right: 120

I'm guessing this is not good. I did this test with only one spark plug removed at a time. Does that make a difference or should all of them be out when doing the test? Also, does the engine need to be warmed up?

 

[reiddo1]

Update: I went back and warmed the motor up and ran the test again with all spark plugs removed and updated the results below. One cylinder is measuring half of what the others are. Also, the motor smokes quite a bit more than normal.

Here are the results of my compression test on all four cylinders:

Top Left: 120
Bottom Left: 120

Top right: 60
Bottom Right: 120

I'm guessing this is not good. I did this test with only one spark plug removed at a time. Does that make a difference or should all of them be out when doing the test? Also, does the engine need to be warmed up?

YES to both questions. It is essential to have all plugs removed to have the highest cranking speed. A cold engine may not allow for proper ring sealing and usually results in slightly lower compression values. Unless you have a lot of carbon buildup on the rings, your 60 psi cylinder is reason for concern.

 

[emdsapmgr]

Your 60 compression reading is bad. Normal acceptable compression variance is 10% from the high cyl to the low. Basically, your 60 cylinder is not really providing any contribution to running the engine. Possible that you may be lucky. If the head gasket is bad, that could explain a bad cyl. Pull that head off and check the seal ring around the outer edge of that gasket. If it's not continuous, replace it. Sometimes when the seal ring goes bad, it could let a little water into that combusion chamber... Could be an easy fix. Also: when the head is off, you'll want to check to see if the top ring is still intact on that piston and to see if the cylinder liner/piston show any signs of scuffing. A bigger problem.

 

[Silvertip]

Do a "Decarb" and the low compression may come up. Low compression may be due to rings stuck due to excess carbon build up.

 

[racerone]

Remove the cylinder head for inspection !

 

[steelespike]

check the impeller also the thermostats.

 

[sutor623]

Ouch, sorry to hear this Jason. That #1 cylinder is the highest one on the block and tends to be the first one to overheat. Also highest carb so a sluggish fuel pump will lean that cylinder out first. I am anxious to see what is going on under the cylinder head.

 

[emdsapmgr]

As you pull the head, I'd also pull the carb apart that feeds that cyl with the 60 reading. Do an autopsy on that carb throat. Remove all the jets and check them visually for any debris, or restriction. Any restriction will limit fuel flow and as well the amount of oil that gets to that cyl. Long term running lean will slowly degrade the compression as the cyl destructs. Pull the head and check for piston crown damage and for cyl liner scuffing.

 

[fhhuber]

The plugs are oil fouled... could be excess pre-mix or an oil that isn't burning right if 2-stroke... oil getting past rings or valve stems if 4-stroke.

I'm not up on which are which by model number.

For compression test I run the engine just enough for the block to feel slightly warm, then do the test.
One being way off is a bad sign. (as noted by others)

Check the thermostats for debris interfering with cooling. Fortunately for me, my thermostat started leaking and had to be replaced... there were bits that got past the intake strainer stuck in there. That leak may have saved the engine.

 

[racerone]

3 plugs look normal and one plug does not.--Plugs go black like that when there is no heat produced to keep them clean.----That might be because of low compression.--Post pictures of the bad cylinder / head gasket !