Topic: 1956 Johnson 10HO QD 19 exhaust housing temp – Page 5

This topic has 50 replies, 11 voices, and was last updated 6 years, 10 months ago by bob-d.

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July 16, 2017 at 2:52 am #61676
bob-d
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US Member
Don thanks for looking around. The 2nd one would be perfect, but at 80 bucks delivered a bit much.
The Evinrude one I’m not sure about, as the guy lists it as a 68 with the right part number 377447, but no 10HPs were made that year?
After doing some research I am thinking this exhaust housing might have been a problem design, and the OMC engineer design staff fixed it after 1958, because the part number 377447 is a one year number only. This might have been a result when they lighten the 10HP by 7 pounds vs.the 1957 ?
Maybe Garry or Frank would know?
July 16, 2017 at 1:34 pm #61688
fleetwin
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US Member - 2 Years
Well yes, this hsg is a one year only piece….But, this is only because of the lower motor cover change. 1958 was the only year of the 10hp/small g/c and exhaust hsg that used the aluminum clam shell hoods, later models all used the one piece lower motor cover and fiberglass hood. The change in the exhaust hsg is the mounting holes/flanges on top of the hsg for the different cover/hood design that occurred in 1959.
And yes, the seller is incorrect, that is surely not a 1968 10hp, no such thing.
Were there other problems with the 1958 exhaust hsg design? Not to my knowledge, but maybe Garry/Frank might know more. I do remember one other fellow having a problem similar to yours, but I think it was on a 10hp that was a 59 or newer model. I’m pretty sure the fix was adding a very small bleed hole at the top of the inlet water tube passage to spray the upper hsg with cool water….
This is an interesting topic for sure, would love to find the actual fault with the hsg…I will have to have another look at the hsg I have….
I would speak with the fellow with the Johnson hsg, I’m betting he is willing to accept much less, his asking price is ridiculous, he is just shooting for the moon.
July 16, 2017 at 3:04 pm #61693
bob-d
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US Member
Don, picked up an 58 Evinrude exhaust housing for $25. Ok so it’s blue……..might just burn the paint off it anyway!
Stay tuned.
July 16, 2017 at 3:38 pm #61697
fleetwin
Participant
US Member - 2 Years
OK, still looking for you Bob…
I am very interested in this topic now….
The way I see it, either the exhaust hsg is defective causing this condition….Or, perhaps the powerhead has some sort of cooling relief in this area we are not aware of causing this strange symptom….I guess we will know real quick once you try a different exhaust hsg….
Sure wish I had the right one to give you in an effort to get to the bottom of this situation….
July 16, 2017 at 4:59 pm #61703
opposedtwin
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US Member - 2 Years
Aren’t the FD and QD towers the same size? I thought the legs (including the gear case) were the same for these two models. If they are, I have one off a 1957 FD you can have for shipping.
Scott
July 16, 2017 at 5:18 pm #61704
fleetwin
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US Member - 2 Years
quote opposedtwin:

Aren’t the FD and QD towers the same size? I thought the legs (including the gear case) were the same for these two models. If they are, I have one off a 1957 FD you can have for shipping.
Scott

Unfortunately, this is only true up to 1957. In 1958 OMC trimmed costs by adapting the small midsection/gearcase used on the 5.5/7.5 models to use on the 10hp…He is looking for a 1958 10hp midsection, which is a unique part to that year….
July 28, 2017 at 10:13 pm #62343
fleetwin
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US Member - 2 Years
OK, finally got back home and was able to dig into this situation further….
First, I examined a 62 QD exhaust housing. I clamped the housing into a vise vertically, then jammed a fuel hose onto the bottom of the copper water tube. With the long fuel line above the top of the exhaust hsg, I slowly filled the hose with water until the water was just about level with the top of the exhaust hsg cooling intake passage. I did not see any water leaking out of what we guessed might be an intake water bleed off to help cool the exhaust hsg. So, that theory does not appear to be the case.
Next, I found a 1958 Sportwin powerhead, and had a closer look at it. I looked closely at the casting area around where the cooling water enters the powerhead, but saw no evidence of a cooling water bleed off. Next, I had a look at the rear of the powerhead where water exits into the exhaust hsg. I DID find a horizontal cooling water bleed off that is directed into the exhaust hsg, I’m thinking the hole is between 1/32-1/16" in diameter. Like I say, the hole is horizontal, although I’m thinking it is probably angled down just a bit to help cool the exhaust hsg. The exhaust chamber is open into the forward area as well, so I’m guessing this bleed helps keep the forward area cool as well. It should be noted that I found this same bleed hole on an FD powerhead as well…
I will work on posting some pictures tonight…Don
July 29, 2017 at 12:49 am #62351
bob-d
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US Member
Don, traveling right now, and can’t check my motor, but boy that sure looks like the answer to the overheating if mine is clogged. That bleed hole would definitely cool the exhaust temp way down. Great detective work. Thanks for all the "exhausted" work on the problem!
Bob
August 1, 2017 at 2:07 am #62468
bob-d
Participant
US Member
Update, just checked my powerhead, and could barely find the bleed hole that Fastwin mentioned. It was buried under layers of carbon.Took over an hour with dental picks and small drill bits to open it up. I’m 100% positive that this is what caused the problem. I would have never found the bleed hole without Fleetwins help. Thanks again. I will provide an update again once I get it back together, and give it a test run in the tank.
August 1, 2017 at 2:23 am #62470
1946zephyr
Participant
Well, one thing I have noticed, is the drain holes on these older motors are pretty small. They tend to plug up too easily and you have to keep after them. This is a new case to me, though. In 25+ years of outboard tinkering, I have never heard of that drain hole. It might be beneficial to open it up a bit, to reduce the clogging potential, wouldn’t it? I see later motors went up to 1/4" or bigger, for gearcases. Not many late models clog up anymore. It would be worth it, to look into this option. Carbon works quickly, clogging up holes that small.
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