Topic: 67 33HP Evinrude running very hot – Page 2 – Antique Outboard Motor Club,Inc

This topic has 33 replies, 7 voices, and was last updated 2 years ago by fleetwin.

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July 24, 2023 at 9:04 am #278438
fleetwin
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Well, I guess anything IS possible. At this point, I would like to have a closer look at the exhaust hsg cavity where the little bleed hole dumps into. Where does this cavity lead to? Is there a passage from this cavity into the upper part of the exhaust hsg that should help cool it? Take some more pictures of the exhaust hsg and that cavity.

Like Frank says, an air/exhaust leak into the water pump could be to blame, but it doesn’t seem as though the powerhead is actually overheating, although you haven’t actually checked with a pyrometer yet. It is easy to pull that side cover off (provided the screws will come out) to check for the crack Franks pictured. May as well pull the gearcase off to have another look at the impeller/hsg and the mating surface below it. But, I’m remembering that you said it had good water flow, so that pulls me away from the air/exhaust leak into the pump theory a bit. Although it would still probably pump well at low speeds because that area is under water, even with an air/exhaust leak. Looking at the pump discharge at high speeds would give a better indication.

Finally, there is surely the possibility that this engine is cooling “normally”/as designed, and that exhaust hsg area just normally gets hot. I suppose we could consider adding a cooling bleed hole somewhere if none is to be found. But, we must be very careful to avoid re-engineering the wheel and creating other problems. I just wish I had some of these style engines laying around to tear into, but don’t…

Finally, please use new gaskets when you reassemble, don’t mess around with the old ones, even though they are almost new, especially the head gasket.
July 24, 2023 at 11:18 am #278451
bob-d
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Thanks everyone.
Frank thanks for jumping in……..hey at least it wasn’t an oil question. 😃.
I’ll start digging into the gear case and check the water pump / impeller / overall flow. Although when I rebuilt the motor I replaced most of the parts to err on the side of caution. I did have flow when I noticed the steam water mix, possibly not strong enough? Don’t remember if I used a Chinese knock off impeller or a OMC? Will definitely try the barrel power drill method to check water flow, thanks Jeff for the idea.
Frank, my lower unit is getting red hot exactly in the same spot as the picture of the junked motor, interesting.
I’ll also pull the intake cover plate and look for a crack.

I have so much (more than it’s worth) invested in the motor. After having a number of questionable motors in the past, my plan was to build at least one super reliable motor for my main boat. I’m on a very large lake , and breaking down 5 or 6 miles out is no fun. This was going to be my go to motor. Just get in turn the key and drive…….. well at least not yet.
Thanks again,
Bob D
July 24, 2023 at 3:26 pm #278457
Michael Brown
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I have a 1958 Johnson. I had water cooling problems. I took off the thermostat cover and ran the motor. Out the small tube I got exhaust pressure and smoke. The repair manual states if there is an exhaust leak into the system it will not cool. You may even have good compression readings and it will not pump. After much frustration we took the power head off checked all passages and nothing. Turned the driveshaft in a bucket of water with a drill and got great flow. Upon taking the head off found 3 head bolts only finger tight. Replaced the head gasket torqued all the bolts down and water pumps great. ANY LEAK around the head gasket and it will not pump water. Im happy now but it was frustrating. It takes a long time running for these motors to pump water when you first start it up. That is my experience, hope it helps.

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fleetwin
July 24, 2023 at 3:59 pm #278458
fleetwin
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bob-d wrote:

Thanks everyone.
Frank thanks for jumping in……..hey at least it wasn’t an oil question. 😃.
I’ll start digging into the gear case and check the water pump / impeller / overall flow. Although when I rebuilt the motor I replaced most of the parts to err on the side of caution. I did have flow when I noticed the steam water mix, possibly not strong enough? Don’t remember if I used a Chinese knock off impeller or a OMC? Will definitely try the barrel power drill method to check water flow, thanks Jeff for the idea.
Frank, my lower unit is getting red hot exactly in the same spot as the picture of the junked motor, interesting.
I’ll also pull the intake cover plate and look for a crack.

I have so much (more than it’s worth) invested in the motor. After having a number of questionable motors in the past, my plan was to build at least one super reliable motor for my main boat. I’m on a very large lake , and breaking down 5 or 6 miles out is no fun. This was going to be my go to motor. Just get in turn the key and drive…….. well at least not yet.
Thanks again,
Bob D

Chances are pretty good that the barrel/drill test won’t tell much, I’m sure you will see flow out of the impeller housing. Needless to say, I would avoid the chinese knock off impellers at all cost, replace it with an OEM. Let’s have a closer look at the exhaust hsg cavity where underneath the cooling bleed hole.
July 24, 2023 at 4:05 pm #278459
fleetwin
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US Member
Michael Brown wrote:

I have a 1958 Johnson. I had water cooling problems. I took off the thermostat cover and ran the motor. Out the small tube I got exhaust pressure and smoke. The repair manual states if there is an exhaust leak into the system it will not cool. You may even have good compression readings and it will not pump. After much frustration we took the power head off checked all passages and nothing. Turned the driveshaft in a bucket of water with a drill and got great flow. Upon taking the head off found 3 head bolts only finger tight. Replaced the head gasket torqued all the bolts down and water pumps great. ANY LEAK around the head gasket and it will not pump water. Im happy now but it was frustrating. It takes a long time running for these motors to pump water when you first start it up. That is my experience, hope it helps.

It is important to note that seeing that smoke come out with the thermostat cap removed is usually normal. This is because exhaust pressure is making its way back upn through where the cooling water exits the cylinder head into the exhaust housing, escaping through that little passage under the thermostat cover. Your theory could be correct if the smoke was exiting through the passage where pressurized water enters the thermostat hsg, but this is very difficult to confirm on these engines.
July 24, 2023 at 10:48 pm #278471
bob-d
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US Member
Don, here is a picture of the exhaust housing cavity you asked for. I removed the square plate and exposed a large bleed hole that I guess is what the engineers planned to cool the exhaust housing using the water that dumps from the rectangular opening on the top of the picture. I did a lot of digging and that was the only bleed hole I could find on the exhaust housing.
I will remove the plate that Frank mentioned tomorrow and look for a crack . Other than that I’m out of ideas. I will heed your advice and purchase all new OEM gaskets when I put it all back together. That will go for a new impeller as well.
Only problem is that my vacation is over this weekend. Unfortunately I won’t have time to rebuild and test the motor until next July, as the boat and motor are stored at my vacation home. I’ll take the head, and gear case home with me and continue probing. I won’t be able to reassemble and water test until next July. It’s going to be a long year thinking about the problem.
Thanks again,
Bob D
July 25, 2023 at 10:30 am #278482
crosbyman
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Canada Member
not much to clog on the exhaust bottom end of things…

have to tried pulling the PH and feeding water in the entry point of the water tube and then checking to see where and how much water exits the engine cavities …back out to the outside world ? check the thermostat flow channel seems it should come out as fast as it goes in if proper cooling is expected from the water pump.

if all is ok… recheck the impeller and pump assembly & cavities below

Joining AOMCI has priviledges 🙂

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bob-d
July 25, 2023 at 12:30 pm #278487
bob-d
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crosbyman wrote:

not much to clog on the exhaust bottom end of things…

have to tried pulling the PH and feeding water in the entry point of the water tube and then checking to see where and how much water exits the engine cavities …back out to the outside world ? check the thermostat flow channel seems it should come out as fast as it goes in if proper cooling is expected from the water pump.

if all is ok… recheck the impeller and pump assembly & cavities below

Crosbyman , water comes up the water tube and fills the cavity under the exhaust cover.
There are some picture in some of my first posts which show the bleed holes. From there it goes out to the water jacket around the cylinders. Everything flowed nicely when I put water through the passages. No thermostat on this motor.
Thinking ……just thinking all this might come down to a cheap impeller, possibly not pumping enough volume at slow speed when I initially saw the water / steam coming out of the discharge. I really can’t find anything else wrong on the motor, and I have certainly disassembled and gone through every piece of it!

Bob D
July 25, 2023 at 12:32 pm #278489
crosbyman
Participant
Canada Member
well if top side is ok… check impeller flow rate again… patience brings joy 🙂

Joining AOMCI has priviledges 🙂

1 user thanked author for this post.

bob-d
July 26, 2023 at 6:59 am #278508
fleetwin
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US Member
OK, so all the water exits the powerhead through that cavity in the back. Somewhere there must be a larger hole in the powerhead cavity where the water leaves the head, hard to tell from your picture. That little bleed hole underneath the powerhead is surely not large enough.

So you found a little bleed hole where a little water leaves that rear ex hsg cavity and sprays inside the housing to cool it, am assuming it was clear. Some engines have a little bleed hole on the intake water tube as well, but who knows if this is one of them. Just wish I had a similar exhaust hsg to disect to get all the answers to our questions. Hopefully one will turn up before you reassemble.

So sorry about your vacation, but I would just hate to have you put the whole thing back together with the old gaskets only to have leaks develop. I was under the impression that there was plenty of water flow when you saw the steam coming out, but maybe I misread the post. So, it is best to pull that pump apart to see if the impeller is OEM. Did you replace the impeller hsg and SS plate during the rebuild? None of the impeller cover threads were messed up in the gearcase? Mating surfaces good underneath the SS plate?

As always, anything is possible here, so sorry you pulled that powerhead apart Bob. D
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