New member with a F9.9 MSH2D cooling water problem

[doug25427]

I have a used 2005 F9.9 MSH2D (4 stroke) outboard which appears to be in good shape. This is the first time I have attempted to start it after the original owner test ran it for me.
I have changed the fluids, filters and spark plugs.
Today I started the outboard with rabbit ears on the water intake.
For the first 4-5 minutes I had an adequate stream of water from the pee hole but it suddenly stopped entirely.
I shut the engine down immediately as I was right there when it happened. No high temperature damage happened.
I figured I had a water pump impeller to replace so I dropped the lower unit and found the impeller needed to be replaced. I ordered the kit and since I have a few days to wait on the parts I decided to check the water hoses for obstruction.
This is where I am getting confused.
First I disconnected the rubber hoses at the T fitting located on the left side of the bottom cowling. One of these hoses went to the pee hole, another went to the exhaust outer cover hose fitting and another went through a fitting in the bottom cowling towards the water pump I assume.
I used low pressure air to blow through the hose leading to the pee hole finding it open and unobstructed.
Next I blew through the water pump tube at the end of the lower cowling where the water pump mates to the water tube. I expected air to come out of the hose connected to the fitting on the bottom cowling. I used a hose which fit the water tube tightly so there was no air leakage around the water tube when I applied low pressure air to the tube.
Instead of air coming from the hose connected to the fitting on the bottom cowling it was coming from the fitting at the exhaust outer cover.
This make no sense to me.
I assumed the water pump pushes water through the water tube towards the engine so I should have felt air pressure through the hose attached to the fitting in the bottom casing.
I have looked over the parts diagrams for this outboard and I can not explain how air pressure entering into the water tube at the water pump can find its way to the outer exhaust cover fitting.
Can someone help me out?

[boscoe99]

The rubber hoses typically don't have anything to do with the supply of water that is sent up to the block from the water pump. Water goes first to the base of the block and then up through the block and head itself. Some of that water is bypassed to the pisser and other areas.

Go to the Yamaha Parts Catalog and you can get a better feel for how the water system works. Better still would be looking at your service manual.

[doug25427]

The rubber hoses typically don't have anything to do with the supply of water that is sent up to the block from the water pump. Water goes first to the base of the block and then up through the block and head itself. Some of that water is bypassed to the pisser and other areas.

Go to the Yamaha Parts Catalog and you can get a better feel for how the water system works. Better still would be looking at your service manual.

Being you are a senior member I am hesitant to disagree with you however I have triple checked the rubber hose routing.
I have been using the correct online parts diagrams for this outboard and a service manual I found online which is not the correct manual for this outboard. Its close but not correct.
I have ordered an OEM service manual but was told it would be at least 2 weeks getting to me.
My thought is a broken water tube.

[99yam40]

the water tube that leaves the water pump is a metal one I am sure.
here is something that shows it with the rubber seals at the ends.
2005 F9.9MSH2D Yamaha Outboard LOWER CASING DRIVE 2 Diagram and Parts

I am not sure what the other rubber hose goes to though as I have not worked on one like that before

[boscoe99]

Being you are a senior member I am hesitant to disagree with you however I have triple checked the rubber hose routing.
I have been using the correct online parts diagrams for this outboard and a service manual I found online which is not the correct manual for this outboard. Its close but not correct.
I have ordered an OEM service manual but was told it would be at least 2 weeks getting to me.
My thought is a broken water tube.

The number of ones posts means nothing. Just might mean that I BS more than others.

Don't be hesitant at all to disagree with me. If you find that I am wrong come back and let me know of your findings. If I am wrong I will say so and apologize.

[doug25427]

the water tube that leaves the water pump is a metal one I am sure.
here is something that shows it with the rubber seals at the ends.
2005 F9.9MSH2D Yamaha Outboard LOWER CASING DRIVE 2 Diagram and Parts

I am not sure what the other rubber hose goes to though as I have not worked on one like that before

That is one the diagrams I have been looking at. It shows the water tube extending upwards from the water pump. I assume the other end attaches to the fitting in the bottom cowling.
When I blow low pressure air through the water tube at the water pump end it DOES NOT exit out the opposite end as it is shown in this diagram. The air comes out of the outer exhaust cover fitting.
This is very strange as the diagram clearly does not indicate any physical connection between the water tube and any other area.
This is why I believe there is some sort of break in the tube. Maybe the air is escaping and finding its way to the exhaust through the lower casing?
If I had a manual I'd remove the lower casing to check the tube.

[doug25427]

The number of ones posts means nothing. Just might mean that I BS more than others.

Don't be hesitant at all to disagree with me. If you find that I am wrong come back and let me know of your findings. If I am wrong I will say so and apologize.

That's cool.
I have been a joining forums for the last 20 years it seems and have found them to be the number one place to go when I have a problem. I am new here but I am not new to forums.
I am one to have service manuals for everything I own. Some of those manuals have cost me over $250. I believe having them for reference is a must.
Once I join a forum to find an answer to a problem I use the search feature first to see if the problem has already been answered. In the case it has not been.
Many times the answer is simple and starring me in the face. Helpful forums members who have been there and done that can save a lot of time work and aggravation.
I have some skill as a mechanic but I am far from an outboard mechanic. I suspect most of the members here are like me.
When I apply air to one end of a tube I expect air to come out of the other end. When it doesn't work that way I get confused...

[boscoe99]

Water goes up the pipe in the mid-section from the lower unit to the base of the block. Water then flows into the block and the heads. From the block and possibly the head there are tubes that allow water to flow to other places. One being the tell tale. Another tube goes to the garden hose fitting. Another tube may go to the exhaust cover so as to interject water flow into the exhaust to cool things down a bit. In some motors tubes lead to an oil cooler, a VST cooler or a rectifier/regulator cooler.

If air is blown up the water transfer tube then it is going to go into the block and it can then make its way to any of the tubes. It would not be abnormal for air to exit the exhaust since air would be introduced into the exhaust system at the exhaust cover.

Unfortunately there is no diagram from Yamaha that depicts water flow throughout the system for the ingress point to the egress points.

[doug25427]

Water goes up the pipe in the mid-section from the lower unit to the base of the block. Water then flows into the block and the heads. From the block and possibly the head there are tubes that allow water to flow to other places. One being the tell tale. Another tube goes to the garden hose fitting. Another tube may go to the exhaust cover so as to interject water flow into the exhaust to cool things down a bit. In some motors tubes lead to an oil cooler, a VST cooler or a rectifier/regulator cooler.

If air is blown up the water transfer tube then it is going to go into the block and it can then make its way to any of the tubes. It would not be abnormal for air to exit the exhaust since air would be introduced into the exhaust system at the exhaust cover.

Unfortunately there is no diagram from Yamaha that depicts water flow throughout the system for the ingress point to the egress points.

A water flow chart would answer this question quickly.
While the online parts diagrams are not a replacement for the service manual they do provide some information. I was able to determine the rubber hoses were routed on mine as they should be.
On mine water leaves the pump through the water tube upward to a rubber hose fitting in the bottom cowling. A rubber hose attaches here and extends to the left side of the engine to attach to a T fitting. From the T fitting one rubber hose is the pee hole supply and the other attaches to a fitting in the outer exhaust cover.
There is another rubber hose coming out of the outer exhaust cover which leads to a garden hose fitting but this hose has nothing to do with the water pump circuit.
As far as I can see there are no other cooling water hoses or piping.
I may not be an outboard mechanic but common sense tell me I should feel air coming from the end of the water tube when I apply pressure to the opposite end.
I am going to research the procedure for replacing the water tube. If I can get a look at the tube I think I'll find some answers.

[doug25427]

Water goes up the pipe in the mid-section from the lower unit to the base of the block. Water then flows into the block and the heads. From the block and possibly the head there are tubes that allow water to flow to other places. One being the tell tale. Another tube goes to the garden hose fitting. Another tube may go to the exhaust cover so as to interject water flow into the exhaust to cool things down a bit. In some motors tubes lead to an oil cooler, a VST cooler or a rectifier/regulator cooler.

If air is blown up the water transfer tube then it is going to go into the block and it can then make its way to any of the tubes. It would not be abnormal for air to exit the exhaust since air would be introduced into the exhaust system at the exhaust cover.

Unfortunately there is no diagram from Yamaha that depicts water flow throughout the system for the ingress point to the egress points.

It appears your original thought was correct.
Being the closest Yamaha service center is more than 2 hours away I decided to tear into the outboard myself to figure this out.
It took me about 30 minutes to remove the upper portion of the power head from the lower portion. Once I had it off I discovered the hose fitting in the bottom cowling was not singularly connected to the water tube.
I didn't have to remove the bottom cowling or the lower half of the power head to know the water tube connects to the lower half of the power head not the bottom cowling hose fitting alone. The lower half of the power head is mostly the oil pan but has passages for cooling and exhaust.
My theory is the cooling system is set up like this because it is a 4 stroke. Unlike a 2 stroke where the water cycles from the pump nonstop without a thermostat a 4 stroke has to have alternative pathways for the cooling water when the thermostat closes.
Maybe I don't know what I'm talking about... being a seat of the pants outboard mechanic I probably am wrong.
Oh well... I'll put the power head back together, get the water pump fixed and see what I have then.

[cleddau1]

?thermostat

Water and in the test low pressure air will only come out of the rubber hose on the side of the head in any quantity when the thermostat is open, and under the test conditions it will be closed. Try removing the thermostat, worth doing anyway as often clogged with junk..

[rodbolt17]

the 9.9 had a peculiar issue.
look at the two water hoses that nipple to the side of the cyl head.
remove those two hoses from the nipple.
apply air to the nipples and pray that it blows through.

if it does not you have two basic options.
1 is remove the head.

two is contact me.