Yamaha 9.9 cooling water flow?

[Brian P.]

I just bought a boat with a 9.9 Yamaha which had no water flow. I replaced the water pump and now have water flow out of only the top discharge pipe on the port side of the motor. I would expect water to come out of both pipe nipples. Both discharge pipes are connected by tubing to the discharge port at the cowling. Does anyone know if both ports should be discharging water and if so how I could clean it out. I've tried blowing air in it to blow any debris out and also inserting a small wire but no luck. This motor was used in salt water and sat for some time so it may just be clogged up. Any and all ideas are appreciated.

Brian

 

[sdsaw]

Re: Yamaha 9.9 cooling water flow?

You are on the right track in guessing that it is clogged. When I had mine apart a lot of the cooling passages had salt build up. I flush the motor after each use but I think that the design of the cooling passages doesn't allow for the water to flow freely (too many dead end spots)
I wouldn't worry about it. I can bet that there are many 9.9 Yamahas out there that have this same condition, including mine

 

[Brian P.]

Re: Yamaha 9.9 cooling water flow?

Thanks for the reply sdsaw. The lower cylinder temperature is too hot to leave it the way it is. I'm hoping to find something that will disolve the deposits or remove them without disassembling the motor. Water does drip out of the lower port and an occasional chunk of some white deposit. What did you have to remove to get to those water passages?

 

[sdsaw]

Re: Yamaha 9.9 cooling water flow?

I had the motor disassembled to fix some corrosion issues and cleaned it out then.
You say that you are getting some flow? I think that is a good sign that the blockage may not be too bad.
You may want to keep trying the compressed air route.
There are some products that are supposed to break down salt deposits such as Salt-X and Salt-away. If you can soak the passageways with those products it may help.
Beware of any products that may be too strong and damage the aluminum and be gentle on those brass tubes that the hoses slip over because I broke mine but was able to repair them with some solder.

Hey, get this. After cleaning all the cooling passages, I had to tear back into the motor(about 3 months) and found some of the passages were getting salt build up already! This occurred even though I flushed the motor after saltwater usage even using Saltaway. Even now my top tube has no water flowing from it.
I'm not going to worry about it because I mostly use it for slow trolling(running at a high idle)

If you ever have any running issues with that motor, suspect the carb.,float bowl and jets first(I speak from experience)

BTW, what year is your motor?

 

[Brian P.]

Re: Yamaha 9.9 cooling water flow?

sdsaw, Thanks for the ideas. I'm not sure what year the 9.9 is although I think it may be a 1997. It's mounted on a 1990 22' Grady White that was repowered with a 1999 225 Mercury Optimax.

I've connected a piece of clear tubing with the salt away inside and let it sit for about 4 days now. I haven't noticed any improvement. I thought about taking the little brass fitting off so I could insert something to clean the internal passage. But you say that it broke off. So I assume it doesn't unscrew?

Did you take the motor apart or have someone else do it? If you did it what did you have to remove to get to the blocked passage. Is it just that back cover/plate? The shop manual I have does not show the cooling water passages like the Mecury manual does.

thanks again, Brian

 

[sdsaw]

Re: Yamaha 9.9 cooling water flow?

Brian,
I think the brass fitting pressed into the head. The part I broke was the small tube the comes off at 90 degrees but was able to repair it with lead solder. If you really want to remove the fitting to gain better access to the passage you can carefully grip it and pull on it while rotating and it should pull out, but...I take no responsibility if this doesn't work out. You can reinstall the tube using some lock-tite or JB Weld if it does not feel tight enough.

As far as disassembling the motor to clean the blockage, I believe you have to separate the head from the block to get to the cooling passages. The back plate that you were referring to contains the cam and rocker arms.
If you are serious about working on the motor yourself you should invest in a Yamaha factory service manual which will cover only your model and year. Much more detail and will show you where the cooling water flows thru the motor. It helped me repair mine.
You know I have a much older model than yours so if some of the things that I am describing doesn't make sense this is probably the reason.
Good luck with it.

Scott

 

[dancamp009]

Re: Yamaha 9.9 cooling water flow?

I've got a 92 Yamaha 9.9 high thrust that I have had lots of trouble with salting up. Two years ago I took it apart and cleaned it out as best I would and put it back together, but it's already salted up again even though I run water through it after every use.
When I recently started it after it sat all winter it wouldn't pump any water, so I took off the two brass nipples and found lots of salt in there. I then removed the valve cover and found an area where I could drill two holes into the ports and then tap a hole for a brass plug to remove again later on. I drilled out a lot of salt from both ports which worked wonders on the bottom (rear) port, but the top (front) port is still not pumping water, and I drilled all the way down the port three inches or so. I also dripped muriatic acid into the ports to dissolve the salt, which worked wonders on the rear port, but still hasn't fixed the front port.
The front port now pumps water like I've never seen before though, so I'm happy about that. I wish I had a schematic or picture of how the water travels through those ports in that head so I could find where the plugged water port is from the outside. I would then consider drilling into it from outside to clean it out then tap and plug the hole or add a nipple for water to eliminate from that hole.
Why doesn't Yamaha solve this salting up problem by giving us better access to these water ports? They probably just want to sell more new motors. But I would be afraid to buy any salt water cooled outboard after this problem.

 

[catsailor07]

Re: Yamaha 9.9 cooling water flow?

I just got a high thrust 2001 9.9 and have had problems twice with starting. First time I changed the plugs and it went, last Sunday morning it wouldn't start and I cleaned and gapped the plugs still wouldn't start. Late in the day around 4:00pm I tried again and it fired up and ran ok. Now I should mention I put 500 miles on the new plugs running all day long (40-50nm a day) running canals and locks pushing a 6,500 lb sailboat then it sat idle for two weeks.

Any thoughts? I've got a supply of new plugs now just in case.

John