Topic: 1976 Johnson 35HP carbon buildup – Antique Outboard Motor Club,Inc

This topic has 8 replies, 7 voices, and was last updated 8 years, 1 month ago by huppster.

Viewing 9 posts - 1 through 9 (of 9 total)

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June 5, 2017 at 2:17 pm #7243
huppster
Participant
I recently had to take the cylinder head off my 1976 35HP Johnson. I noticed that the bottom cylinder has a fair amount of carbon buildup while the other is pretty clean. Can anyone help me understand why this would happen and is there anything I can look at to correct the issue?

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June 8, 2017 at 11:36 pm #59297
joesnuffy
Participant
What is the reason you took off the cylinder head off. Was it a rebuild? Did you ever hear this engine run and use it? Just curious why you took cylinder head off? Must have been some issue.

Joe
June 9, 2017 at 4:21 pm #59352
huppster
Participant
I have had it running well recently. I hit a patch of seaweed that caused it to overheat. The head gasket sprang a water leak. I’m not sure if there is any more damage but so far it looks like only the water leak.
June 9, 2017 at 5:36 pm #59354
fisherman6
Participant
US Member
Was the water leaking near the top cylinder? Any water getting into the cylinder certainly could have washed away the carbon buildup that was there. It may have looked just like the bottom cylinder before a little water got in while running.
-Ben

OldJohnnyRude on YouTube
June 10, 2017 at 10:02 am #59381
billw
Participant
US Member
quote Fisherman6:

Was the water leaking near the top cylinder? Any water getting into the cylinder certainly could have washed away the carbon buildup that was there. It may have looked just like the bottom cylinder before a little water got in while running.
-Ben

I will second that one. We used to see leaks such as yours develop into small, eroded channels for water in the aluminum, if the blown head gasket was not brought to our attention as a performance issue by the owner, in time. It is really amazing just how clean the water will eventually wash away the carbon, especially on that particular family of engines.

Long live American manufacturing!
June 10, 2017 at 1:56 pm #59391
johng
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US MEMBER PAY BY CHECK
Is the bottom electrode bent? looks like it
June 10, 2017 at 3:47 pm #59404
garry-in-michigan
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Lifetime Member
I think that is distortion caused by the wide angle lense. . . 😀
June 11, 2017 at 12:45 am #59441
fleetwin
Participant
US Member
Be sure to check the rubber cooling deflectors in the block as well. Unfortunately, these engines are prone to overheating, especially with the water pick ups right in front of the gearcase where they are easily plugged with bags/seaweed. I’m assuming you have the gearcase off as well to do a water pump job. I wouldn’t worry about the different combustion chamber appearances too much if the engine was running/idling OK before the overheat problem.
June 11, 2017 at 8:13 pm #59479
huppster
Participant
Thanks for the advice. I hope to have it back together soon.
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