1967 Johnson 6hp water on spark plug despite good compression and performance

[zephemeros]

I have a 1967 Johnson 6 horse, runs great and starts on the first pull even when cold, idles very low and never misfires.
I decided to pull the spark plugs today to see how they look after some recent heavy usage, and the bottom cylinder plug looked great, however the top cylinder plug was covered in water and had some milky grease on the electrode. Looking inside the cylinder it appears normal and I see no scoring on the walls, only a bit of carbon buildup, maybe a bit more than the bottom cylinder has. Compression is 85 psi on the top cylinder and 87 psi on the bottom.
It is possible that some condensation/water may have been in the gas, but not so much that the plug would be filled with water, or so I thought at least. I would think that such a large amount of water in the gas would result in poor performance anyway.
Could this be a head gasket issue despite the reasonable compression readings, or should I be looking elsewhere? Or is a bit of water in the cylinder normal and not something to worry about?

Thanks!

 

[Rays14ft.]

Compression sounds low to me. My 67 Fisherman would blow 115. My guess is that the head is warped or gasket failed letting in water. Cheap fix if just a couple gaskets.

 

[F_R]

Head gasket or exhaust cover gasket. OR--it has been turned upside down since last time it was ran. It is remarkable that it runs well with water in cylinder.

 

[HighTrim]

Compression sounds low to me. My 67 Fisherman would blow 115. My guess is that the head is warped or gasket failed letting in water. Cheap fix if just a couple gaskets.

You definitely have a faulty gauge. The Fishermans were no where near that high compression even out of the crate. 85 psi is very normal, and good compression.

That being said, still check for faulty gaskets and ensure no water is getting into cylinder.

 

[oldboat1]

That motor has kind of a wonky thermostat mount and cover, in my opinion, and somebody may have done some overtorquing up there. It's conceivable (if unlikely) that there is a hairline crack down to the top plug hole in the head cover. If the ceramic part of the plug is getting wet or some moisture under the boot, though, it may be some kind of crack in the head cover. If not the t.stat cover bolts, maybe the head bolt up there was overtightened in concert with a leaking thermostat gasket. People do crazy stuff.... Maybe a PO fix.

Your compression seems fine (have run them OK with quite a bit less). It wouldn't hurt to replace head cover and exhaust gaskets, though, resurfacing both -- and look for any hairline cracks. Stretching for an explanation, but think you are pretty much locked into taking a look at the covers anyway, and reseating them. Good maintenance, anyhow.

Is there moisture in the plug threads? If the plugs are loose or the washers gone, that could allow some moisture in the threads, but would look for it to be coming from outside -- maybe a freeze plug leaking water, or water in the pan after sitting out? Didn't get dunked or catch a wave over the transom, did it? Trolling motor running low on an auxiliary mount? And....is this a salt water motor? Some salt corrosion causing issues somewhere?

 

[zephemeros]

I in fact did turn the motor upside down when I took it off the boat, probably moreso than I usually do. Seeing as how I've never seen any water in there before, could this actually be the cause?
Thanks for the detailed responses, I really appreciate the suggestions.
I'll probably be taking it out tomorrow so I'll try not to turn it upside down when I take it off and see if there's still any water in there.

 

[F_R]

Absolutely. Water works by gravity. If the underwater exhaust housing has water in it and you turn it up to where the lower unit is higher than the powerhead, that water runs where gravity says it should go--which is into the exhaust ports in the cylinders. Come back three weeks later and find the motor is junk from all the rusted parts in the powerhead.

 

[oldboat1]

whoa. got the cause and the culprit! Might spray some fogging oil into the cylinders and pull it over a few times with the plugs out, then clean up plugs and run it some more (more running is better, I would think). Think I would fog it this year when storing it, even if not your normal practice.

But I'm sure an awful lot of small motors get similar or worse treatment, and survive OK. Think of all those motors wedged in car trunks every which way after vacation trips, then stored badly up in garages until the next year.