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1984 Mercury 60hp 3cyl water in top cylinder

N

Noelie84

Member
Good evening.
I've got a problem with water intrusion into the top cylinder (only) on my 3 cylinder Mercury. Yesterday i had it out on the water and it started fine, putzed away from the boat launch fine, ran perfectly for two miles up the lake at probably 2/3 throttle, and then I throttled back to troll and it suddenly wouldn't idle. Getting it back was a pain, but once it managed to get past 2500 rpms or so it ran fine again all the way back to the landing, where it repeated its 'no low rpms' performance for a crowd while I tried to maneuver in to dock.

I have good compression in all 3 cylinders, but the top cylinder isn't firing and fouls the plug in no time. No scoring in the cylinder, fortunately. I didn't overheat it that I'm aware of (new water pump last summer, lots of flow through the telltale, and it's warm but not hot) but I figured maybe head gasket anyway. But I pulled off the cover on the spark plug side and apparently rather than a head that's just the cover to some sort of water jacket thing that I wasn't anticipating, lol. So before I started stripping my motor down, I figured I'd beg on here for some advice.

Pros:
1) While I had that cover off, I checked and didn't see any cracks or holes in the cylinder ?tops? where water could be leaking from
2) There was no fuel/oil residue in there either
3) No scoring, holes, or other damage to the cylinder wall or piston that I can see
4) Compression, spark, and fuel supply all are good; the bottom 2 cylinders run like champs.
5) I'm mechanically inclined and have been wrenching for years (just not on outboards)

Cons:
1) Water is definitely getting into the top cylinder; grey-white sludge on the plug is a dead giveaway. Switched the plugs around and tried again with it on the muffs to make 100% sure, and it fouled the top plug again
2) Motor does not have the head-block-gasket setup I was expecting, so I'm in uncharted waters here
3) I have no idea where else water could be infiltrating that cylinder from
4) I am not a Meatloaf fan, so as far as I'm concerned 2 out of 3 IS bad.

Can I get an assist? Does this motor have a head gasket (or even a head?) If so, where would I find them to check them? Also, where else could water be getting into this cylinder from? Is there a water jacket on the crank /carb side too, for some reason?
 
That's the only place water could be entering, other than in the fuel itself. That cover you removed is just the water jacket.
 
There have been issues with the top cylinder cracking around the sparkplug hole.-----May not show up on a cold compression test.----Something for you to consider.
 
racerone said:
No head gasket.----Look for water leaks on the exhaust cover gasket.
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Ok, will do. I'll pull that cover tonight. There's a water passage under there? Seems like an odd place for one.

timguy said:
That's the only place water could be entering, other than in the fuel itself. That cover you removed is just the water jacket.
Click to expand...

And boy was I surprised when I popped that plate off! :confused:

faztbullet said:
Exhaust gasket or chipped/broken reed
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Where are the reeds on this motor? I'm assuming they're behind the carbs where they're supposed to be?

fastjeff said:
Hopefully it's a bad exhaust plate gasket, but it could also be a cracked cylinder--I've seen one.

Jeff
Click to expand...

racerone said:
There have been issues with the top cylinder cracking around the sparkplug hole.-----May not show up on a cold compression test.----Something for you to consider.
Click to expand...

I was able to get a good close look around the spark plugs while I had that back plate off, and didn't see any cracks or damage; the whole thing's actually very clean in there so I think it would have been pretty easy to spot. I'll have to look underneath the exhaust plate this evening after work and see what I find.


Thanks everybody! I appreciate the guidance.
 
I stripped everything down last night. You all made me nervous about cylinder cracks, so I popped that back cover off again and went over everything in there with a bright light and an inspection mirror, but I can't see any evidence of a crack anywhere in there. It all looks pristine, honestly.
So I moved on to the exhaust plate, and I think we might have found a winner. The gasket didn't have any cracks/breaks that I could see (I broke that piece that's sticking up so I could get a picture of the underside of it), but it wasn't adhered at all to the plates and there was a spot that definitely had a clear channel of moisture/oil sludge underneath it.


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I cleaned up the plate with some carb cleaner and a brush and I can't find any defects in the metal, so hopefully it's just the gasket. I've got a fresh set on order that should be here by this weekend. I'll post an update after I install them and test it.
 
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Looks like that's it. What do you think about a LIGHT film of 518 Loctite gasket eliminator on each side of your new gasket? This is the same stuff used for crankcase halves sealing. The 518 is perhaps a bit better for aluminum applications over the 515. Best to let set for 24 hours. There could be a little deflection in the surface here too. If thats the case, the Loctite will fill the imperfections.
 
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Ok, so I got everything reassembled Saturday afternoon, but I couldn't find the torque specs anywhere online. How tight should these bolts be? Just 'hand tight' with a ratchet, or do they need to be torqued to X ft/lbs?
 
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