1973 50 hp Johnson - Possible water in cylinder

[JoeFromAkron]

73' 50 hp Johnson - Runs great, spark is good, haven't done compression test yet this year. I have had an issue with with a white/grey film forming on the plugs. They do not look steam cleaned. It has fouled the plugs twice on me now. Once on Lake Erie which was pretty dangerous as I almost got pushed up on a breakwall before it finally started and once at the dock.

The first time it fouled was also the first time I used the gaped plugs (ql77jc4) as the motor had Surface gap plugs when I bought it so I left them in as it ran fine. I checked the plugs several times last year and never noticed this film before I put in the gaped plugs. Low and behold this year I have the film again, this time on the surface gap plugs and it wouldn't start second time out. I put in a set of the gaped plugs and it fired right up. Checked the gaped plugs and they have this film on them again but started and ran fine.

So I think the white/grey film I am getting is some kind of water/oil mix. Its not a lot if it and if it didn't keep the plugs from firing I probably wouldn't think twice about it. The motor does not appear to have ever overheated and the water pump is new and working fine as far as I can tell. Passes the "Hand on hot engine for three seconds" test at least. I am imagining the head gasket has failed? I have the proper tools so that would be easy to fix I think.

Could incomplete combustion cause this also? I did a spark and compression test when I got it and it was fine but everything's gotta break sometime. It appears to have the original coils and power pack but the stator is seemingly not original.

Also, when if first happened I thought "I got water in the gas" and this spring I hooked up a external fuel fiter/water separator. So with new fuel and the filter, I think I can rule out water in the fuel.

Thanks for any advice.

 

[Joe Reeves]

Yes, the white grayish wet stuff is normally water that has worked its way into the fuel system somehow.

Water in the fuel is east to detect... simply drain fuel out of the fuel hose into a glass container. If water is present, it will be obvious as the two elements separate... water is heavier so that will be the bottom liquid.

Stop putting it off and take a compression test. What are the psi readings of the individual cylinders?

 

[JoeFromAkron]

Thanks a bunch for the reply. I don’t post here much but I read it all the time. Obviously you know your stuff.

I just did the compression test. 93 on top cylinder and 95 on the bottom. There was no visible water on the plugs from warming it up first but that was only a short time running. I know it’s not water in the fuel tank though. I’m running this off a properly cleaned tank. Last year I suspected water but I always clean the tanks out in the spring. Plus added a water separator I should have had anyways.

 

[racerone]

Those compression values are way too low.-----Possible blown head gasket.

 

[JoeFromAkron]

‘‘Tis my thought also. A blown head gasket could cause water water in the cylinder also, right?

 

[racerone]

A good one would read about 140 PSI on my gauge.-----I would remove cylinder head first.

 

[JoeFromAkron]

A good one would read about 140 PSI on my gauge.-----I would remove cylinder head first.

I don’t know how good my gauge is. It’s just one I got on amazon but I am thinking that since I have a symptom of a blown head gasket and compression is seemingly low... well I should have at it. I have an inch pound torque wrench. Do I need to worry about the cylinder head cover gasket also? I’ve only done head gaskets on smaller older motors that are one piece. I’m just gonna replace the thermostat also.

 

[racerone]

You will need both gaskets.

 

[JoeFromAkron]

Both gaskets, new thermostat and thermostat gasket have been ordered. From Iboats of course. I am not supposed to use any kind of sealant on the head gaskets, correct?

 

[Joe Reeves]

Correct... No Sealant.

 

[JoeFromAkron]

Awesome. Will report back the results in a couple of days.

 

[Bosunsmate]

Plane the head while its off on some glass covered with sandpaper or a mirror, thats what i use. i think thatl fix your issue with it

 

[JoeFromAkron]

So I took it out this weekend up to Lake Erie. Weather was fine and I wanted to confirm this was water getting mixed in before I do the gasket change. New plugs and it ran fine. Actually the boat ran faster than last year for some reason at WOT. It did stall once on the lake but turns out it was becasue of a kinked fuel line. I naturally assumed I had this water/oil mix fouling the plugs so I took them out. There was none of this film on the plugs and they looked fine to my surprise. I discovered the primer bulb was flat and the line was kinked at my water separator. After I remedied that all was well. All together I ran over 10 miles mostly at 3/4 throttle. Question is shouldn't I expect to see this film on the plugs even after running at fast speeds? I know there was not water in the gas tank before, at least I am 99.9% sure.

 

[Joe Reeves]

It's possible that when you got around to checking the fuel for water.... that whatever was there had been expelled. Hopefully you are one of the lucky ones. Time will tell.

 

[JoeFromAkron]

I didn’t just check the fuel for water. November last year was the first time the issue presented and last time I had the boat out until spring. This spring I drained and cleaned my tank. It’s just a portable 6 gal. So fresh fuel mix. I also added a water separator to make sure I kept water out of the fuel system. The first time this year it fouled the plugs again but I never ran it for long and only at idle. After that it seems fine.

Hopefully I am just lucky! I don’t want to take the head off unless I have to. I guess if it happens again at least I will have the gaskets handy.

 

[JoeFromAkron]

So I decided to not be a lazy jerk and do the work. I’m very glad I did. All the bolts came out easily. The head gasket was ok, I think, but the motor got the new one. The water jacket gasket was not. I don’t know how long it was leaking but it was in bad shape. Obvious leakage and was falling apart while simultaneously stuck to the head. I had to sand it off. There was something like mineral deposits where it was leaking to the cylinders in several spots.

Most alarming was the thermostat. It was in pieces. The top cap on it had corroded away and was in a water passage. Rusty looking crap all over. It had to have been like that for a long time. The thermostat gasket was intact and I am 99% sure I got all the pieces.

The cylinder walls were luckily not corroded or damaged in any obvious way. There were rust stains in the oil/water mix on the walls but no chunks and they were wiped off with a rag coated in 2 stroke oil. Pistons in good shape. Got it all cleaned up/leveled and reassembled with the new thermostat. I didn’t get a chance to fire it up but it should be fine. It’s fairly obvious after this is where the water leakage was coming from. I know internal corrosion is going to be a concern. Hopefully it will be ok but time will tell I guess?

 

[Bosunsmate]

They are robust, should be fine. Turn it over to get some oil into the bearings

 

[Bosunsmate]

Remember to re torque after first heat cycle too (when its cooled down)

 

[JoeFromAkron]

Remember to re torque after first heat cycle too (when its cooled down)

My Plan is to run it in a barrel for an hour or so tonight, re-torque, then take it muskie trolling this weekend to do the rest of the break in time. My understanding is that it should be run 5 hours at no more than half throttle? I was telling a guy at my work that this is something of a testament to the general ruggedness of these motors that mine ran as well as it did with this damage. If it hadn't started fouling the plugs I never would have known.

 

[JoeFromAkron]

So I got to run it tonight in my barrel tonight. Started right up but didn't want to stay running at first without the warm-up lever being raised. Before it stayed running without it. Confirmed the thermostat seems to be working. It takes about a minute and the water increases coming out of the ports in the back. Mine does not have a tell-tale. I have read about how to install one so I may do that in the near future. Anyways, I thought maybe I broke something else so I tested the spark gap. All was well there. Mine can jump about an inch on both. After that it was good to go though. It stayed running without the warm-up lever being up. I turned it off 3 times to see if I was getting noticeable water on the plugs and I don't think I was. Certainly not like before. I also did a compression test and both cylinders were at about 105. That's higher than before but maybe my tester is just crap. At least they are even, right? I'm gonna let it run for a while in the barrel tomorrow night to make sure I'm not getting any leaks and saturday I'm gonna go do the break in. I'm pretty happy and extremely grateful for the help received here.