Topic: 1956 Johnson 10HO QD 19 exhaust housing temp – Page 3

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

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June 27, 2017 at 12:40 am #60429
bob-d
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Chris, found the spray vent 1/2 down and it was clear. The more I look at it I am leaning towards the idea that the gasket was shot, as there is carbon buildup towards the front of the engine,and all over the internal shifter assembly. I believe a good gasket would have keep the combustion localized and directed it down.Ordered a new gasket from Dan Gano. Will report back once installed. Fleetwin will also try to look under the mystery SS cover. I just dread breaking off the screws. Lots of heat,PB Blaster and my impact hammer.
June 27, 2017 at 7:37 am #60442
frankr
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I don’t think you will find anything below that SS cover. But then I didn’t expect you to find all that carbon either.

The drive shaft on that motor runs in it’s own isolation tube. Depending on a good gasket at top and the tube above the water pump to maintain the isolation from the exhaust. Drain holes near the lower mount drain off any water that escapes the pump housing at the drive shaft hole.
June 27, 2017 at 1:13 pm #60458
johng
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US Member - 2 Years
I had a 56′ Lark RD. that had Mouse renters move in and brought 31 pieces of "Dog Food " up the exhaust leg and into the exhaust cover for a long stay. You better start looking deep on that one.
June 27, 2017 at 2:14 pm #60464
jeff-register
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US Member - 2 Years
Look again at the base gasket. I think someone ahead of this owner pulled the powerhead & never used a new base gasket in return to the tower.
June 28, 2017 at 1:34 am #60503
bob-d
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Well I got the mystery plate off and Frank was right. Not much to report. Just a large open casting. It did have a rather large hole from the main water exhaust that probably cools off the exhause on the way out. On the bottom anothe small vent. Everything clear. No real carbon buildup, no mice homes or dog food reserve.
So my only hope at this point is the new gasket. What is the best sealer for it and the new head gasket? The old standby, OMC gasket sealing compound?
June 29, 2017 at 1:19 pm #60588
johng
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US Member - 2 Years
The exhaust housing cover is supposed to be water cooled. There is a stainless steel plate under it ( to route water). check to see if the plate is there and then see if the plate has any holes in it. Holes can re-route exhaust. You may NOT have to pull the exhaust cover off-look inside with the power head off.
I think I have a plate and both gaskets here. please e-mail scj616@aol.com
July 13, 2017 at 2:04 pm #61525
bob-d
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US Member
Following up on this problem. Put a new base gasket on, and tried it on the boat vs.test tank. The exhaust housing under the shift lever still got so hot that it turned the water to steam. I’m at a bit of a loss?
Could the exhaust housing become damaged, where the exhaust stream gets rerouted, since now I know the base gasket is good?
My next thought would be to take the exhaust housing off the powerhead, and check all water passagees. On initial rebuild I installed new impeller and used compressed air to check the water passages through the head. All seemed fine,and water is coming out exhaust hole 1/2 down exhaust housing.
Anyone have any new ideas?
July 13, 2017 at 9:30 pm #61555
fleetwin
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US Member - 2 Years
Well, this is a strange case indeed…You mention doing a rebuild, was the housing discolored like that prior to the rebuild, or did this condition occur afterwards…
This is strange only because the area that is getting so hot is not an area that is really exposed to hot exhaust, all the hot exhaust is on the other side of that exhaust housing rib that divides those chambers. Yes, the exhaust can back up into the forward area, but only after it hits the aft compartment…So, you would think that the aft compartment that is exposed to the hot exhaust first would be the area that might heat up excessively…
I’m looking at your latest picture and see something I would question…That triangular exhaust compartment on the bottom of your picture seems to be opening into the forward area that is getting so hot….I’m wondering if this is some sort of casting flaw….I will have to look at one of my FD exhaust housings to see if it looks the same…
One final question, is the exhaust housing paint burnt on both sides of the exhaust housing, or just on the side shown in your picture??
July 14, 2017 at 3:03 am #61587
bob-d
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Thanks Fleetwin, the exhaust housing was burnt on that side when I got the motor. The other side of the housing remains warm, not boiling hot. Strange how the hot exhaust goes down and makes a right hand turn? Maybe I will just pick up a new exhaust housing, as they are relatively inexpensive?
The motor has 90psi on each cylinder, in addition to the new power head base gasket, it has a new cylinder head, and gasket (bad top plug thread), new impeller, all new seals in lower unit and water pump, new points, coils, and a carb rebuild. Starts and idles well but after running a few minutes it starts to cook.
If anyone has a 58 or later QD exhaust housing I would love to see a picture as maybe it does have a casting defect, or possibly a section of casting broke off? Who knows what could have happen in its 59 year life span.
July 14, 2017 at 12:20 pm #61595
fisherman6
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US Member - 2 Years
After looking at your last picture and reading fleetwin’s post, I believe he is on to something. The side where it appears there is an opening between the two compartments in the exhaust housing and I believe it is on the side of your exhaust housing that has all the paint burnt off. If there is an opening between these two sections in that vertical partition just below the powerhead, that is not supposed to be there. I bet all your problems go away if you swap out that midsection. I had two 1959 Evinrude 10s apart over this past winter and I do not remember there being any kind of opening in that partition. I don’t have any pictures right now, and I’m sure this will be resolved before I get into another one unless I’m working on one at Tomahawk in a few weeks.
-Ben

OldJohnnyRude on YouTube
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