Topic: 1956 Johnson 10HO QD 19 exhaust housing temp – Antique Outboard Motor Club,Inc

This topic has 50 replies, 11 voices, and was last updated 6 years, 9 months ago by bob-d.

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June 25, 2017 at 7:22 pm #7430
bob-d
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US Member
Just resurrected a 10HP Johnson. On first start up noticed where the paint was already discolored was blistering hot. Is this normal for this model. Engine runs and pumps well. New impeller etc. Did not pull the head to inspect yet. Does this have something to do with the baffle, or possibly I need a new gasket under the head?
Also what would cause gas to come up and spill out of the plunger, when under pressure, on the 1956 tank that came with it?
Thanks
June 25, 2017 at 7:41 pm #60309
bob-d
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US Member
Sorry……wrong year it’s a 1958 motor with a 1956 tank.
June 25, 2017 at 7:46 pm #60310
chris-p
Participant
Holy Schmokes! Not supposed to get that hot!

Time to pull off the powerhead. In fact, I see a lot of corrosion and overheating signs. I would pull all of the covers (bypass/head/exhaust) clean, dress, install new gaskets and ensure passages are clear. Something is going on in the leg though, and you wont be able to properly fix without pulling powerhead off.
June 25, 2017 at 7:46 pm #60311
chris-p
Participant
Regarding the tank, you need to change the diaphragm and rebuild.
June 25, 2017 at 7:57 pm #60312
bob-d
Participant
US Member
Chris, will pull head. I think the corrosion on the powerhead was where a mouse family decided to pee. When I originally got the motor there was a nest there.
Rebuilt the gas tank, used a new gasket and diaphragm, and those ridiculously expensive washers under screws.
June 25, 2017 at 8:22 pm #60313
frankr
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US Member
About that diaphragm: The end of the push rod where the diaphragm support washers go must be square and flat. If the metal is corroded away, it certainly will leak. Likewise, the support washers must be flat and not rusted. If distorted, you can flatten them with a tap of a hammer. Finally, use a dab of fuel-proof gasket sealant on the end of the push rod where the support washer meets it.
June 25, 2017 at 8:22 pm #60314
david-bartlett
Participant
What are you running for a fuel mix?
June 25, 2017 at 8:30 pm #60319
frankr
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US Member
Kind of odd that the heat damage is on the forward side of the exhaust housing. I’m thinking there should be a web in there to prevent the flame from going there. Time for a looksee.
June 25, 2017 at 8:49 pm #60320
bob-d
Participant
US Member
Thanks everyone for the suggestions. Tearing the head off now, will post pictures of what’s under there.
Dave running 24:1. The discoloration on the exhaust housing was there when I bought it. Don’t know anything about the motors history. New points,plugs,coil,rebuilt carb etc….Compression is good, starts and idles down well, just that housing is hotter than hell.
Stay tuned.
June 25, 2017 at 9:09 pm #60321
chris-p
Participant
Curious to see what is going on there.

I put a dab of 3M 847 where the rod goes through the diaphragm. Im assuming you have the metal primer button on your tank?
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1956 Johnson 10HO QD 19 exhaust housing temp

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