1956 Johnson 10HO QD 19 exhaust housing temp

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Bob D
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1956 Johnson 10HO QD 19 exhaust housing temp

Postby Bob D » Sun Jun 25, 2017 3:22 pm

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
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Bob D
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Re: 1956 Johnson 10HO QD 19 exhaust housing temp

Postby Bob D » Sun Jun 25, 2017 3:41 pm

Sorry......wrong year it's a 1958 motor with a 1956 tank.

Chris_P
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Re: 1956 Johnson 10HO QD 19 exhaust housing temp

Postby Chris_P » Sun Jun 25, 2017 3:46 pm

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.

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Re: 1956 Johnson 10HO QD 19 exhaust housing temp

Postby Chris_P » Sun Jun 25, 2017 3:46 pm

Regarding the tank, you need to change the diaphragm and rebuild.

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Bob D
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Re: 1956 Johnson 10HO QD 19 exhaust housing temp

Postby Bob D » Sun Jun 25, 2017 3:57 pm

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.

FrankR
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Re: 1956 Johnson 10HO QD 19 exhaust housing temp

Postby FrankR » Sun Jun 25, 2017 4:22 pm

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.

david bartlett
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Re: 1956 Johnson 10HO QD 19 exhaust housing temp

Postby david bartlett » Sun Jun 25, 2017 4:22 pm

What are you running for a fuel mix?
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Re: 1956 Johnson 10HO QD 19 exhaust housing temp

Postby FrankR » Sun Jun 25, 2017 4:30 pm

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.

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Bob D
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Re: 1956 Johnson 10HO QD 19 exhaust housing temp

Postby Bob D » Sun Jun 25, 2017 4:49 pm

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.

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Re: 1956 Johnson 10HO QD 19 exhaust housing temp

Postby Chris_P » Sun Jun 25, 2017 5:09 pm

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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