Just changed the impeller, and gaskets in the leg of my 90 HP Yamaha.
Thought I would give it a good flush out , so i removed the thermostat and poppet valve, and put the leg in a drum with 70 cm deep water.
I have never run the motor in a drum previously.
To my surprise, the pump did not push water through the exhaust jacket, and there was no telltale.
I had previously run it on muffs, with no issues or over heating. Telltale was fine
So while in the drum, i connected the side flush up to a hose, and primed the exhaust section, and restarted the motor.
Everything went well from there.Tell tale was working great Run it for 20 minutes, no overheating at all.
So had a break, and come back an hour later, and the same issue..Had to prime the top end again.
This happen 3 times over the day..
Have I done something incorrectly with my first ever drum flush???
I will put the poppet valve and thermostat back in place to complete the process.
There has been no over heating during this issue.
Any ideas. PS The water level was higher than the water pump..david
just an idea, you did put the little locating pin/whatever it is called into the impeller. it fits into a groove on the shaft. I have had it come out with the impeller and dropped it and had to look for it, with out it your shaft will spin but not the impeller.
All good with the woodruff key . Pump is working fine, just needs to be primed from the side hose connection at the top, to get the tell tale to indicate. So in the drum the water doesn't get to exhaust manifold, from where the tell tale runs unless i fill it firstly. Then it runs perfectly. Could be because I have the poppet valve and thermostat removed.
I have never flushed the motor from a drum previously. Once I filled the exhaust manifold, ran perfectly in the drum for 20 minutes. Did a good flush out actually.
David
Good outcome, I've never run a motor without either poppet or thermostat removed. Motors are quirky things, last trip on way home motor sounded noisier, had a vibration which was very noticeable around 2K rpm. Took my mechanic for a run today and it ran perfectly. Figure maybe a bit of carbon got caught somewhere and caused the plugs to misfire, after cooling down and starting up again it fell off and now it's a Kodak Moment - waiting for something to develop.Originally Posted by dnej
Chances are you had more water pressure on the hose than the water pump was generating. Poppet valve would normally be closed at idle - it opens under higher speed (higher water pressure) and could well have been directing enough water where it normally wouldn't be going at idle to stop the tell tale. Refit it and try again.
A water pump should pump water at any engine rpm since the impeller is submerged it self primes the water galleries right through the system usually a thermostat is at the top or near the top of the powerhead
If its not pumping water your missing a seal, the base gasket/seal is leaking on the water pump, or the housing are worn from u running a the engine with no water flow
When the drive shaft goes up thru the waterpump housing there is a rubber seal around the driveshaft the friction along with no water is enough to melt the water pump covers the water than under pressure just circulates thru the elongated melted pump base plate
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Hello DNEJ,
Is this motor a two stroke Yamaha 90?
It’s all because the poppet valve was removed it closes at idle low rpm to allow for the lower pressure from the water pump
good to remove it as they can corrode and not seal on the aluminium seat for the valve
as already has been said the drum provides no positive water pressure just like sitting at idle on the water
the muffs work because of the tap water pressure and some engines will even give a telltail stream without the engine running on tightly sealed muffs
Thanks everyone. Yes a 90 HP 2 stroke Yamaha.
The impeller is fine, and pumps normally once the exhaust chamber is primed with the hose connection.
I thought the poppet valve might be the problem, and today I am flushing again in the drum, with priming the exhaust chamber first, after that I will be replacing the poppet valve and thermostat and retry just to confirm that all is OK.
Just out of interest, if i had left the motor running, would the exhaust chamber, and consequently the tell tale eventually fill up?
David
the drums as same as having the boat on the water, as long as the drums deep enough.
ive got one and the water sits well above the cav plate
the tell tale should be instant after the motor starts
Hello everyone, Steve j, I meant with the poppet valve and thermostat removed.. all good
My report for those who have not done this exercise. The result was a success, with about 1.5 egg cup lot of shell grit sand and what ever else was flushed out.
Some thing I learnt. The water pump cannot self prime, so the water level must be up around where the water pump sits in the leg.
The place where you would normally put the muffs is not the level you want.
Lower the front of your trailer when inserting the drum, and don't put the water in first, as you need to manoeuvrer the drum while lowering the motor. Then raise the front of the trailer, to get the motor as low as possible in the drum.
Remove the poppet valve, and thermostat, to increase the water flow.
Dont expect the tell tale to work as normal, with the poppet valve and thermostat removed, as discussed above.as the water will not be in the exhaust jacket/manifold, and so the tell tale cant work. I primed this area with my side flush hose link.
I added vinegar to the water, and ran the motor for 20 minutes at a time, with brakes in between. Use a bucket to catch the tell tale water.
After you are happy with the flush, remove the vinegar water and flush thoroughly again with clean water.
So with a new water pump kit installed, and the pump working well, the pressure gauge on the water passage on the head was indicating 5psi, so that is where it normally is sitting. Sits higher than that when travelling of course.
Just be advised that this motor has only done 48 hours, and has been flushed on muffs regularly after each use.
Say with a 50 degree thermostat opening temperature, does anyone know what temperatures the water jacket over the head would be. I just bought myself a thermometer.
By the way, when I installed the poppet valve and thermostat, the telltale ran normally, so the above comments were correct.
David
I think i have read outboard thermostats open at around 75c just what i have read, car engines open at 90c water boils at 100c
Just remember if u sligtly offset your flushing muffs on any outboard and u run the engine and she doesnt pump water there is a chance u can melt the water pump housing, mercury actually show u pictures of how a impeller perishes without water over 30sec 1min 2min 3mins etc.. a dry impeller is cactus after a few minutes they also show u the idle speeds for the dry impeller pictures
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Name your source, link required or I call BS.Just remember if u sligtly offset your flushing muffs on any outboard and u run the engine and she doesnt pump water there is a chance u can melt the water pump housing, mercury actually show u pictures of how a impeller perishes without water over 30sec 1min 2min 3mins etc.. a dry impeller is cactus after a few minutes they also show u the idle speeds for the dry impeller pictures
Call bs all you like try downloading a mercury workshop manual and take a look for your self
It was in my 50hp mid to late 80's manual found it while looking for advanced timing specs
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I can't recall ever seeing anything like that put out by Mercury Gazza but I'll keep a lookout for it.
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