1979 Johnson 25hp - Overheated - please help with next step

[bbryan36]

My first post. I've been lurking for a while. The info I've found on here has been great, but i finally have a specific question.

Got a new job a few months back running a different auto shop where we work on outboards from time to time. They quickly showed me the importance of "peeing" and i realized that i don't think my boat had been peeing in some time. It was a gift to me 3 years ago and other than clean the carb and change a coil and plugs i never really serviced it.

First I changed out my milky lower end fluid and replaced the water pump. Got it back together and it ran fine. Pee'd strong. I checked the lower end fluid and it was already milky. So i got the two seals needed to remedy that and replaced them. Hooked it all back up and started. Fired up and noticed it wasn't peeing. I cut power and removed the lower unit. I was pretty sure it was hooked up properly but i figured re-doing it to be sure wouldn't hurt. Got it back together again and ran it.

After start up it still wasn't peeing...but i ran it a bit too long i guess and something gave way. I got a streak of very dark oily substance running from the upper part of the engine and it seeped out quickly from the top section of the lower unit on the exterior side. I knew this was not good so i turned off and removed the lower unit. it certainly came from the powerhead area and not from the lower unit.

I still have decent compression on both cylinders - around 110 psi. It takes 4-5 pulls to get up that high, not sure if that is normal on an outboard or if that in itself is an issue. Didn't see any excessive fluid on the spark plug.

Today i removed the power head and got a better look into the inner exhaust tube. I didn't pull the tube off yet, as i didn't see any obvious leaks from the outer side of its seal. The inside of it is hard to see into, so there may still be an issue there.

That is where i currently have stopped and i'm looking to get some advice as to what to look for next. I'm not opposed to pulling anything apart, but i want to have an idea what i should be looking for in terms of the likely culprit. This motor hasn't been taken apart ever so if there are some things i really should do anyways i'm all ears.

Please avoid lectures on running without peeing. I get it. It was dumb. I made a mistake and i understand that mistake is why i'm here. Before running it again i'll run some air through all the passages and make sure they're clear. I just want to get this out on the water!

 

[F_R]

Was the powerhead gasket burned or leaking from the overheat? Much depends on how hot it got. On any outboard that has been significantly overheated, the head gasket and exhaust cover gaskets (on side of powerhead) should be replaced. Failure to do so can allow water entry where it doesn't belong.

 

[bbryan36]

Was the powerhead gasket burned or leaking from the overheat? Much depends on how hot it got. On any outboard that has been significantly overheated, the head gasket and exhaust cover gaskets (on side of powerhead) should be replaced. Failure to do so can allow water entry where it doesn't belong.

If you are referring to the paper gasket between the bottom of the powerhead and the upper part of the exhaust section...No leaks or burns detected there. Gasket was cruddy and very old, but was definitely doing its job.Looked into the water passages and they look fine and clear.

Removed the inner exhaust tube and lower crankshaft housing. Lower crank housing seems fine and was not the source of the leak,

In the image of the bottom side of the power head (which when in the motor is the port side of the motor) there is a pool of the nasty looking oil that was running out. I didn't let it leak for more than 5 seconds so there isn't much there but it was definitely a problem.

I couldn't really get an image of it, but looking into the exhaust section of the powerhead i can see 3 holes on each cylinder on the block. The middle hole on the upper cylinder has a lot of the oil that was leaking on it. The other two holes on that cylinder have a small amount of oil on them as well. The lower cylinder has no oil on any of them.

 

[kbait]

Overheating can also cause the ignition module (CDI box/ brain box) to fail. Sometimes they stop firing on one cylinder only (spark test to confirm). If it's running on one cylinder, the dead cylinder isn't burning any fuel..and it will be expelled out with exhaust..causing an oily/gunky mess. Perhaps that is your issue?
PS.. if firing on one, swap coils .. if spark follows th coil, then bad coil. If not, check for melted/shorting wiring to/from CDI box before replacing it.

Good luck!

 

[bbryan36]

Overheating can also cause the ignition module (CDI box/ brain box) to fail. Sometimes they stop firing on one cylinder only (spark test to confirm). If it's running on one cylinder, the dead cylinder isn't burning any fuel..and it will be expelled out with exhaust..causing an oily/gunky mess. Perhaps that is your issue?
PS.. if firing on one, swap coils .. if spark follows th coil, then bad coil. If not, check for melted/shorting wiring to/from CDI box before replacing it.

Good luck!

Hmm didn't think of something like that. It seemed to be running ok but i was a bit in panic mode shutting it off so i wasn't really paying attention. I'll definitely make sure thats not an issue before i start it up.

p.s. stay strong brother, we have home field advantage this year in the big one. its our time SKOL!