July 28, 2021 at 12:10 pm #243792
I am struggling with a water pumping issue on my 1961 johnson 40, long shaft.
pumps ok initially, maybe 20 seconds, and then slows down and stops. exhaust in the water jacket.
Thermostat in or out doesnt seem to make a difference, thermostat cover on/off doesnt make a difference. Disconnecting the automatic choke to use the hose barb as a telltale shows the same thing (plug off the hose to prevent air entering though the choke). Water for the first 20 seconds or so and then just exhaust puffing out. Running with and without the intake plate/screen on the gearcase doesnt matter.
The impeller, shaft seal at top of water pump housing, driveshaft tube O rings, and all 4 water tube grommets are new. I checked the thermostat in a pot on the stove and it seems fine.
120psi on both cylinders and no sign of water on the plugs.
I checked the gearcase passages and there is no blockage between the water pump and the intake plate that could be starving the pump on the intake side.
I have also tried the old impeller (it looked and felt fine but is at least 20 years old) in case my new one is faulty. No change.
Running in a tank with water up to the lower mounts, the water pump is a good 7″ under water.
The block feels hot to me, I run it until i get nervous about heat and then shut it down to cool. Thinking that the overtemp sensor for the dash light is just a switch, I have it hooked to my multimeter on continuity to watch for it closing. I dont know if it works, but I have not seen it close the circuit before I shut things down.
US Member - 1 Year
Topics: 46July 28, 2021 at 1:43 pm #243794
Is the impeller plate on the water pump sealed tight to the gearcase? If not you could be sucking air. Also, are the water tubes properly seating in the grommets? Any holes in the water tubes? Is the water tube gasket on the pump housing sealed good?
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July 28, 2021 at 4:05 pm #243816
- This reply was modified 1 month, 2 weeks ago by bobw.
I did not apply sealant to the plate or the base of the water pump housing. I will try that. There is no evidence of old sealant there.
I am confident that the water tubes are properly seated and that the tubes themselves are in excellent condition. I have had the lower unit of repeatedly trying to sort this out and have been very careful with tube alignment each time. The water tube grommets are new (top and bottom of the supply and return tubes) and are nice, soft rubber. I believe that they are sealing well.July 29, 2021 at 9:05 am #243848
Give us more on the history of this engine…Is it new to you? If not, did it ever pump correctly? Sounds like you have thought and looked at most everything. Sounds like the gearcase is buried deep in the water also. How did the aluminum impeller housing look? Was the little vent hole clear? You speak of running it with the thermostat in and out, made no difference. How are you determining that it stops pumping water? Is the plastic thermostat housing and check valve/spring in place?
As far as sealing the SS impeller plate, I don’t think that would make too much difference when running the gearcase real deep in the test tank at lower speeds. Good sealing is required when running on a boat at higher speeds when the water level drops and the water pump gets surrounded by exhaust. BUT, you need to check the condition of the gearcase casting underneath the SS impeller plate, perhaps it has eroded away allowing exhaust to be pulled in under the pump. Any evidence of broken water pump screws in the past? Perhaps there was a botched thread repair or something like that creating a sealing problem….July 29, 2021 at 9:46 am #243854
Thanks, Im happy to dig into anything that anyone can suggest at this point.
A little history.
This motor was/is my fathers. He picked it up used maybe 35 years ago. We used it fairly regularly without issues until about 15 years ago when the arm on the throttle broke. Ill get the name wrong, but its the short plate that is peened onto the endo of the rod with the butterfly plate. the plate broke in half at the locking screw. It sat for a few more years and mice got in and made a real mess under the hood. wires and hoses damaged. corrosion from waste. It was taken apart at that time and sat in boxes until this summer when I got sick of walking past it in that state. I repaired the broken part and put the rest of the motor back together. It seems like it is going to run fine. It needs tuning but I have not dared run it long enough to get to that yet.
This motor has seen salt water and there is corrosion on the lower unit. There is also minor pitting on the impeller housing. None of the sealing surfaces of the gearcase, impeller plate, or impeller housing are compromised, I just sealed them together last night so can do another test today. The worst corrosion is around the lowest intake screen, the rolled up part. I will inspect that area closely to look for any direct connection to the exhaust side. Someone appears to have knocked off and welded on the intake side (port) of the ventilation plate. Its a little ugly and some weld burn in has created a few voids around the intake plate that would allow water to go around the plate/screen instead of through. This is unsightly, but I did not think it was a functional issue.
The water pump screws and their holes all look and feel good and original. The shaft has a slight polished groove where the impeller seal rides but not enough to concern me.
As for determining that it stops pumping, my concerns came from lack of any water spit at the exhaust relief (seen in youtube videos of this vintage motor, not 1961 though) and the general feeling that it was getting too hot (based on touch and how quickly water steamed off the block)
I removed the tstat and cover to observe the water flow at the top of the block, this is when I noticed that it would pump ok for a short while and then just slow down and stop. I also checked with everything back together correctly by removing the line that supplies the automatic choke to use that fitting as a telltale. I saw the same thing, water for a while and then just exhaust in little puffs
The tstat holder (black thing), check valve, and ball are in place and look fine. However when I flush water into the drain tube (lower unit off) water comes out the supply tube with seemingly no resistance. That check valve should at least do something? I really dont know what the water path is inside this motor.
I have 2 short videos, one shows flow (and then lack thereof) at the top of the tstat housing without tstat and cover and the other shows the puffs of smoke exiting what is normally the supply line to the automatic choke. I do not know how to share them here.
I have gotten pretty good with the 1956-1958 motors, but this one is different enough that I may not have a good grasp of what it should be doing.
I want to convert this motor to a short shaft. The boat it is on has a very tall transom extension to take the long shaft. Given the condition of the lower unit I will just replace it rather than rebuild it with a shorter shift rod. Its really ugly and needs resealing(and gears/bearings inspected…water may have sat in there), I dont think I can extract the skeg screws intact anyway. I am looking for a donor motor or gearcase locally. I was hoping to get it running and tuned to make sure that the rest of the motor was worth putting money into before I make a purchase.July 29, 2021 at 10:10 am #243855
I took a close look at the gearcase just now. No indication of any path from exhaust to water tubes. The inside actually looks pretty good, if nothing else all that oil kept it coated and slowed corrosion.
Attached are 2 pictures, one shows the corrosion that has eroded around the lower water intake (still no puncture into exhaust tube) and the other shows the burn in from welding at the lower rear of the side intake cover plate.
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US Member - 2 Years
Topics: 22July 29, 2021 at 3:32 pm #243894
Did you check the screen and the area just above it for blockage. The holes in the bypass plate may allow the pump cavity to fill, so that it appears to pump when you first start it. If the screen is plugged up, it won’t allow pumping much above idle for very long. Something to look at?
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US Member - 2 Years
Topics: 13July 29, 2021 at 4:11 pm #243900
My goodness – that’s a pretty rough looking L/U.
Editorial aside — you’ve checked the inputs and from your description, they seem alright. I may have missed some of detail above but what about the outputs ? I.e. are the exits from the port side water jacket plugged ? Is the powerhead base gasket interfering with the water exit from the powerhead?
With a salt water motor – if it’s never been descaled inside, there must be some level of corrosion in the jacket and passages.
If you have a laser thermometer, you can identify the hotspots in the block.
NB. Water spitting or not spitting out of the exhaust relief is not a good measure of waterflow. I have some motors where there is none.July 29, 2021 at 5:22 pm #243908
I was also concerned about an intake clog so I ran it without that plate/screen installed and there was no change.
Need2fish, I am not sure what you mean by outputs? I did my pump flow check with the thermostat out and cover off and water spews out at first and then just stops. Not knowing the water path well, it looks to me like that should be a direct shot from the pump, into the jacket around the cylinders, and then out the hole in the head. With the cover on it should either be directed down to the return side of the pump or out the exhaust.
I also checked at the output near the top of the block that normally feeds the automatic choke, same thing. water at first and then just exhaust puffs.
I have never removed the powerhead, but i suspect that it is a replacement. The block itself just has that flat red primer on it, no top coat present anywhere. All of the other parts are (were) white. If it is not the original powerhead it was replaced more than 30 years ago prior to my father acquiring the motor. I asked him about overheating issues today and he said that he never had any trouble that he could recall.
Would this blockage you mention be something that should be either present or not? As in an installation error or is it something that might develop over time.
The lack of water spitting was just what prompted me to look into it more deeply when I thought it was running hot. The lack of water flow at the thermostat housing and auto choke supply is what really has me concerned. The motor does have the over temp sensor on it which I think is just a switch that will close when it gets hot enough. I dont know what temp that will happen at and I dont trust it yet.
I will track down a thermometer, I know I have one somewhere. My primary concern there is that if the jacket is empty there is going to be less heat transferred to the outer surfaces which could give some false numbers. How hot do I dare let things get? I see the thermostat is 140ish F.
Am I wrong in my thought that without the thermostat installed and with the cover removed, the pump should just spew water out the top? Or that with them both installed, there should be a constant stream from the auto choke supply barb?July 29, 2021 at 6:46 pm #243921
This is the port side of the motor.
circle 1 is the fitting I have been referring to as the auto choke supply. circle 2 is the return.
For my test, I am working with circle 1. I remove the hose and plug it to prevent air entering. I then put a short piece of hose on the fitting so that it terminates above the block. This is where I see the water followed by exhaust and no more water.
You must be logged in to access attached files.July 30, 2021 at 12:38 pm #243968
OK, well I too, am very concerned about the condition of that gearcase…It is badly eroded/corroded from salt or some other electrolysis issue…There may be an issue with the casting underneath the water pump that connects the pick up to the area under the pump….Creating an air leak…This area is full of water when you first start it, explaining why you see water flow for a few seconds…Once started some of the water down there is displaced by exhaust pressure, which may be sneaking its way into the water intake path….I’m not referring to the mating surface between the SS impeller plate and gearcase housing, I am referring to the cast in water passage leading up from the water pick ups. You have tried a new impeller, then reinstalled the old one just in case the new one was NG. Same results with both. You mention the aluminum impeller housing looks “OK”, and you have replaced the seal. There is a tiny vent hole in there that could be plugged though, which could explain this…Sorry, don’t have a picture, perhaps someone else can post one.
OK, seems like you realize that you can’t judge cooling operation from the upper exhaust discharge very well…You should see a continuous gurgling of water coming out of the thermostat pocket while running with the cap removed…Keep in mind that running with the cap removed might just cause most of the water to spill out all over which would explain why you don’t see much coming out of that choke water port…The thermostat housing is upstream of the cylinder jackets. Nonetheless, you have convinced me that the engine has a cooling issue…Water should not stop pouring out of that thermostat pocket with the cap removed running in neutral. Although running the engine in forward gear does help force water up and into the pump…So, a marginal pump could exhibit a condition where the engine pump fine in gear, but fades out in neutral like you describe…
OK, yes, it does look as though someone did replace the engine block, perhaps a powerhead…..But, the engine seemed to cool OK that last time you used it many years ago….But, since that time, mice made a home in there…Mice pee is very corrosive indeed. Was there a mouse nest inside the gearcase exhaust cavity when you removed it to do the water pump job?
And yes, you are correct, that little check valve spring is very light indeed, almost non existent. That check valve is there only to keep the cooling water from “short circuiting” out of the block without circulating through it first…So yes, there would be very little resistance on it. This is a relatively complex cooling system, which is why it has two water tubes….Cool water is meant to circulate back down through the pump to help heat up the water, warm up the engine….
Frank will correct me, or point out more areas to be inspected/checked….
The easiest test for what I suspect would be to install another known good gearcase…I realize this is something you don’t have laying around though….I sure hope I my suspicions are incorrect…DJuly 30, 2021 at 12:46 pm #243969
OK, just thought of something you could try the next time you have the gearcase/pump off….
Remove the side intake plate…Now, find some soft clay or something you could stuff up into the passage that leads up into the bottom of the pump…Please be careful, don’t use anything you can’t get back out of there completely…I sure don’t want you to create another issue leaving clay behind in that passage to really plug things up…Perhaps soft clay is not the best idea, but you understand what I am trying to accomplish. Now, use a syringe/meat baster to fill the cavity under the SS impeller plate, don’t overfill it though causing it to leak over the top. You will see water leaking out if there is some sort of crack or corrosion issue in that passage….July 30, 2021 at 2:49 pm #243977
Ill go through your response in order.
Yes the gearcase is really rough. I am going to replace it once I know the rest of the motor is sound. I also want to make it a short shaft anyway.
I still have the gearcase off so I will inspect those passages again, but as far as I can tell the waste oil coating the inside pretty much prevented any corrosion there despite how ugly the outside is.
After acquiring the motor 30 something years ago, it was a mostly freshwater motor with a seasonal trip to the ocean lasting 4-7 days. It did not live in salt. Electrolysis is more likely. I do know that the wiring on the boat was really rough and usually had issues (now its just gone, problem solved).
The impeller housing has minor pitting but not in locations that could let air in and not enough to leak ALL of the water by the lobes. If I just had low flow I would consider looking for a new housing.
The vent hole is clear, I noticed it when I replaced the impeller. It had been plugged with gunk previously but I replaced the impeller before trying to start the motor the first time. I checked the hole again when I sealed the water pump and it was still clear.
Wouldnt the thermostat housing need to be downstream of the cylinder jacket so that the thermostat was seeing engine temp instead of lake temp?
when I was doing my choke supply test I reinstalled the thermostat and cover to make sure there would be positive pressure in the water jacket.
The mouse damage is ugly but superficial. The metal corrosion is just the surface and will clean up fine. Just a lot of missing paint. I will worry about aesthetics when/if the function is good. They mostly wrecked hoses and wires.
There was no indication of a mouse nest in the exhaust cavity but there were some droppings down inside the lowest area that has to drain out the weep hole. I flushed it all out when I cleaned out the weep hole.
When I was pushing water backwards through the system, I expected the water pressure to force the little check valve shut and more or less stop flow. Chalk this up to me lack of understanding of the water path inside these motors.
I agree, a known good gearcase and impeller would be a great test. I am watching the various local adds and will snag a parts motor or gearcase if I see it. As noted, if the problem is more serious and related to the motor itself I dont want buy a gearcase for an anchor.
I like your leakdown test suggestion. I was letting the sealant cure so the gearcase is still on my bench. Do you think I can do the same test with the housing and impeller installed? I can fill through the outlet and return grommets.July 30, 2021 at 4:51 pm #243985
You can certainly try, I guess you would just have to have the impeller veins oriented correctly. Try it and see if water runs out of the side plate…If it does, then plug the side plate water passage…July 30, 2021 at 4:59 pm #243986
I agree, you don’t want to lay out money for a gearcase if the rest of it is in rough shape….But, just cuz it “looks rough”, doesn’t mean it is…
The water fills the outer exhaust cover first, then is directed down around the cylinder jackets……Once the water reaches the thermostat pocket and fills the cylinders, it is either directed out of the head through the thermostat, or if the thermostat is closed, the water is directed back down the the water pump through that little check valve….
Do I have it “kinda right” Frank??
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