A couple of questions... (Johnson 120)

[Joey]

Motor in question:  1986  120 hp  Johnson J120TLCDC  V4
Compression across all cylinders is 120~
Good fuel, proper 50:1 mix
Tank recently cleaned out, filters clean, new water separator
New spark plugs

When running after a while it seems like it is dropping a cylinder, or like it starts running off 3 instead of four, like a plug is fowling out.  Which is the exact symptom I had before I had the tank, lines and water separator cleaned/replaced and new plugs put in.  

I just checked the gap and it was about .037 which I think is too much, so I reset the gap to .030, also while doing this I noticed that the starboard bottom plug on the power unit was black.  Not burned, or oily, but dark.  The other ones (the material below the electrode which is normally white when you first buy plugs) are a cream or tan color.  Like they have gotten hot, but not black.  The actual electrode was fine and edges where still sharp and nice.  I cleaned it and put it back in.

The motor started right up (better and easier than ever before) and I immediately noticed no water from the pee hole.   And that in the 2 weeks it was sitting idle a nice little dirt dobber clogged it up for me.  I removed the lines and cleaned him out and started it up again, which it did immediately.  I think the gap fixed my problem, which is my first question.

Can improper gap have that effect?  And is .030 proper gap?

Secondly, not a lot of water was coming out of the pee hole.  It was sort of spattering out.  Now I had muffs on the lower unit and they fit good, but a lot of water was blowing out the side (high water pressure).  On all previous outings I did have water coming out the pee hole.  And it never run hot.

Third, I noticed on the port side of the lower unit, where the lower unit meets the upper unit that I had a stream of water about the size of the lead in a number two pencil shooting out the side.

This leads me to the second question.  How bad is this?  I know the lower unit will need to be dropped, and while I am at it I might as well replace the impeller and water pump.  What what else am I looking at?  Is there a seal or gasket here?  What gives with this?

Joey

[seabob4]

Joey, just say starboard side or port side of the powerhead.  We'll know what you're talking about, no descriptions necessary...

[fitz73222]

Joey,
I actually believe the gap is .040 assuming you are using Champion QL77JC4 plugs for your model. Georgie will verify! A black plug usually means weak fire, cold running engine (open thermostat) or a rich condition. Verify by switching it with one of the other plugs and running it to eliminate a bad plug as the problem. I've seen brand new plugs that were defective. If it still runs black, look for a defective coil shorting to ground through the lamination. Again, you can easily switch coils and see if the sympton follows the coil. Try running the engine at night on the flush and pull off the spark plug wire with a pair of plastic fuse pullers and see if the coil starts to do lightining bolts to ground through the coil lamination or the spark plug wire. As far as the water leak at the mating section of the gearcase to midsection it is nothing to worry about. Corrosion at the mating surface or where someone tried to pry the sections apart to drop the gearcase and created a small void at the mating line. There is no gasket or seal, its simply metal to metal mate up and your just seeing water pump bleed off and or some exhaust water discharge. Down here in the southern salt water latitudes its very common and means nothing.

[Joey]

Joey,
I actually believe the gap is .040 assuming you are using Champion QL77JC4 plugs for your model. Georgie will verify! A black plug usually means weak fire, cold running engine (open thermostat) or a rich condition. Verify by switching it with one of the other plugs and running it to eliminate a bad plug as the problem. I've seen brand new plugs that were defective. If it still runs black, look for a defective coil shorting to ground through the lamination. Again, you can easily switch coils and see if the sympton follows the coil. Try running the engine at night on the flush and pull off the spark plug wire with a pair of plastic fuse pullers and see if the coil starts to do lightining bolts to ground through the coil lamination or the spark plug wire. As far as the water leak at the mating section of the gearcase to midsection it is nothing to worry about. Corrosion at the mating surface or where someone tried to pry the sections apart to drop the gearcase and created a small void at the mating line. There is no gasket or seal, its simply metal to metal mate up and your just seeing water pump bleed off and or some exhaust water discharge. Down here in the southern salt water latitudes its very common and means nothing.

Well that was easy.

It is dark, I went out, put the flush on, started the motor, and while standing in the water spewing out from the flush reached up and pulled the spark plug wire.  But I did it with a plastic clamp.  Bet you thought I was gonna get shocked didn't you.  

Anyway, as soon as I did, man the lightning bolts that shot around that coil made for a nice light show.  And they were jumping off the spark plug wire near the coil end all the way to the head.  Nice pretty blue ones.  From what you said, this means a bad coil.

Safe to assume I need to order a new one.  Anything else?

Also, anyone know a place around the gulf coast to get one.  I live 40 miles north of Crystal River.  If not I will order one online.  I found one at MarineEngine.com for $23


Joey

[fitz73222]

I would make sure the coil is from BRP and not a Sierra coil. I just like using OEM electrical parts compared to aftermarket but thats my personal preference. Order the coil from Marine Engine. Did you do the leak test on the other coils while you were at it? There may be others that aren't far behind the one giving you trouble.

[Georgie]

Gap should be .030 (same for almost all older OMC's)

http://www.boatsetup.com/SparkPlugChart.html

they were jumping off the spark plug wire near the coil end all the way to the head. Nice pretty blue ones.

Classic description of a leaking charge!   Glad you were able to locate the problem.

I would make sure the coil is from BRP and not a Sierra coil. I just like using OEM electrical parts compared to aftermarket but thats my personal preference.

agree 150%!!  I do not like aftermarket ignition/electrical components.  Sierra is fine for gaskets and impellers and such, but for critical ignition parts I always go OEM.

[Joey]

You guys are awesome, thanks.

I thought about checking the other coils last night after I came in.  I will do it tonight, and then place an order the ones that need to be replaced.

Edit:

I just decided to buy 4 new OEM coils, 4 new spark plug wire and while I am at it going to drop the lower unit and install and OEM complete water pump kit.  Will be on the hard this weekend doing maintenance.