# Yamaha 5 HP not peeing



## blackshear (Mar 28, 2019)

I have a 2000 Yamaha 5 MSHZ that is not peeing after cleaning out where the dirt daubers had plugged up, both outlet and inlet. I now have the foot apart to check water pump and it was in good shape. I haven’t put it back together yet because I can’t get compressed air to pass through the tube in the foot and out the pee hole. Is it possible that the thermostat is blocking the air? Also before I took it apart I only gave it about 20 to 30 seconds of run time to check the water flow through the pee hole before shutting it down. Should I give it more time to let the thermostat open?


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## DaleH (Mar 28, 2019)

Follow pee hose back to block, remove & check there, hose block exit. 

A t-stat won't open that fast, so I wouldn't run it, also check t-stat & pocket.


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## blackshear (Mar 28, 2019)

This motor doesn’t have a black hose, the exit hole is underneath the block on the bottom side of the engine. I may just put it back together tomorrow and run it on the water hose. Maybe it will pee if given more time for the t-stat to open. I know the impeller is good and the water passage to the impeller is clear.


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## Pappy (Mar 28, 2019)

Then take something like a toothpick or similar and insert it into the hole to clear it. Compressed air if possible. These are usually an indicator that your water pump is working not that your thermostat is opening.


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## blackshear (Mar 29, 2019)

I have cleaned out the passages the best I can with a small wire, air pressure and water pressure. My question is, do you think the thermostat is blocking water flow until the engine warms up? If it’s not too difficult I’m going to see if I can get to the thermostat and make sure it’s not corroded. The previous owner used this motor in saltwater but I have used it for the past 5 years in freshwater. Also it hasn’t been used in over a year now but I wouldn’t think the saltwater would still be causing things to corrode after being used in freshwater for so long.


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## blackshear (Mar 29, 2019)

Well I put the little 5 hp back together and ran it long enough for the thermostat to open and it’s still not peeing. There is a definite obstruction somewhere in the engine. I guess next step is to take a look at the thermostat but it’s a little bit of a pain to get to.


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## Shmelton (Mar 29, 2019)

I had the same problem with a 40hp motor. I pulled the thermostat cover and all,ran it at the boat ramp and all the corrosion came out. I have heard of folks backwashing them with a water hose also. You may have to do it a couple of times. 


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## meonline06 (Mar 30, 2019)

It definitely sounds like you have a blockage somewhere. If you are sure the water pump is good, I would check the thermostat next. If it is stuck closed, it will restrict flow. If it isn't the thermostat, there may be an object blocking flow in the water jacket or a smaller passageway within the block.


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## Shmelton (Mar 30, 2019)

Stupid question, but did you make sure the impeller key is in?


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## nccatfisher (Mar 30, 2019)

I am betting between the dirt dobbers or corrosion you will find your problem will be right at the thermostat. Just as well bite the bullet and take it out and then you can run compressed air from each way.


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## LDUBS (Mar 30, 2019)

Shmelton said:


> Stupid question, but did you make sure the impeller key is in?
> 
> 
> Sent from my iPhone using Tapatalk



Good advice IMO. In this case it sounds like the issue started before he removed the lower unit so that probably isn't it. But still seems like something to check off the list.


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## blackshear (Mar 31, 2019)

Yes the key is installed. In fact I double checked to be sure everything was in place before putting it back together. The more I think about it this motor never really had a very strong stream of water when it was running properly. I’m sure it’s corroion or dirt plugging it up somewhere and hopefully I will be able to clean it out by removing the thermostat. I really don’t want to go into this engine any further. 

The Crappie are biting on the lake so finding time to work on it has been a challenge. I plan to try to get the t-stat out later in today though and will let you know what I find. Thanks


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## Shmelton (Mar 31, 2019)

LDUBS said:


> Shmelton said:
> 
> 
> > Stupid question, but did you make sure the impeller key is in?
> ...



I have heard of them coming out if they aren’t greased properly.


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## blackshear (Mar 31, 2019)

Got the thermostat out today and also took off the head gasket plate. Corrosion was built up in one of the passageways but didn’t appear to be completely stopped up. The thermostat was corroded as well but seemed functional. I have blown air and rammed wire up in all of the passages to try and clean them out. My main concern now is when I blow air backwards through the pee hole I can’t figure out where it is going. It’s not coming back through any of the passages around the thermostat or the head. It’s going somewhere but I’m not sure where. I will keep working with it and see what I come up with tomorrow.


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## Shmelton (Apr 1, 2019)

Run the motor without the tstat in. If water comes out of the hole where the tstat goes you know you are clear from that point back. It will also flush out any corrosion in there. 


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## Shmelton (Apr 1, 2019)

Also if I took the time to pull the tstat and it was corroded I’d replace it. The part on amazon looks to be only about $12-$20. That way you know you won’t have to deal with the tstat for a while.


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## ppine (Apr 1, 2019)

I have a 115 Yamaha that was used a lot at Pyramid Lake, NV by the previous owner. It is not salt water, but close with a lot of dissolved solids. The pee hole was not functioning right. I ran it at idle for 25 minutes with a hose pushing cold water through it. After awhile it freed up and now works fine.


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## blackshear (Apr 1, 2019)

The Thermostat for this engine is located behind a larger plate, it’s not like most engines with the small cover plate for just the thermostat. Maybe I could put it all back together without the thermostat and see what happens. I plan to order a new thermostat today plus gaskets. 

I had no idea that once a motor was removed from the saltwater environment that corrosion would continue to build up. I've used this motor for 5 to 6 years in fresh water only.


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## blackshear (Apr 5, 2019)

With the engine side plate and front cover plate off I cleaned out the water passages the best I could by pushing nylon weed eater string in all of the exposed passages and then blowing them out with compressed air. Then I replaced the thermostat and gaskets with the new ones and reassembled everything. When I started the engine there was just a little bit of water coming out of the pee hole but not much. I blew compressed air backwards through the pee hole and was finally able to get good water flow. I had blown air backwards through the pee hole many times before but this time the foot was submerged in water and I believe it created enough back pressure to help clear out the last bit of blockage. So finally the little 5 hp is back up and running and getting good water flow.

Since I am able to run longer without fear of overheating a new problem has shown up. Now the gas supply is loosing prime after about 5 minutes or so of run time. I suppose the diaphragm in the fuel pump needs replacing. This shouldn't be that bad but looking at the schematic, on boats.net, it shows 2 different diaphragms. Anyone have any experience with Yamaha fuel pumps? Should I replace both of the diaphragms or just the outside one?


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## Pappy (Apr 5, 2019)

Your old thermostat looks to be stuck in the open position.......
As far as the fuel pump goes....you get a complete rebuild kit and do it right.


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## blackshear (Apr 7, 2019)

I also noticed that the thermostat was stuck in the open position after the new one arrived and I was able to compare both of them. It’s just another result from the damage caused by saltwater. Since my last post I have taken the fuel pump apart and decided to replace both diaphragms and gaskets plus a new fuel filter. Hopefully that is all that is wrong with this engine and will get the little 5 hp back in top shape. I have certainly put a lot of time into this engine and it has been quite a learning experience for sure. Thanks to everyone for your help.


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## blackshear (Apr 8, 2019)

The fuel pump parts came today and I was able to successfully put it all back together. The assembly was a little tricky getting the diaphragm spring in place while being blind to properly positioning it with the block of front of it. Somehow it all went together and solved the problem of keeping the fuel primed. This project is done!


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## Pappy (Apr 8, 2019)

The point of my observation about the thermostat was that it was not the source of your overheating. 
If you look back at your post #6 that should become clear. 
Second thing that was never properly determined was the actual operating temperature of the engine and was it ever, in fact, overheating. 
Third, you were assuming that without the overboard indicator working (post from April 5th) that you must have a problem with water flow. Once again, that is no indicator of whether or not there is sufficient waterflow and, in fact, is not necessary at all. All it is there for is to tell you the pump is doing something not how well it is doing. When you think about it, when it was plugged up, there was actually more cooling water passing through your engine! Where some confusion may lie is that the indicator is not the only source for cooling water to exit the block....far from it! The majority of cooling water exits at the base of the powerhead where you cannot see it. 
In your case without the above answers and knowing now that the thermostat was and has been stuck open for a while, your engine may have been cooling all along. 
Having said that, what you did as far as preventative maint. goes was well worth it and you now know a bunch more about your engine! Well done.


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## blackshear (Apr 9, 2019)

Pappy said:


> The point of my observation about the thermostat was that it was not the source of your overheating.
> If you look back at your post #6 that should become clear.
> Second thing that was never properly determined was the actual operating temperature of the engine and was it ever, in fact, overheating.
> Third, you were assuming that without the overboard indicator working (post from April 5th) that you must have a problem with water flow. Once again, that is no indicator of whether or not there is sufficient waterflow and, in fact, is not necessary at all. All it is there for is to tell you the pump is doing something not how well it is doing. When you think about it, when it was plugged up, there was actually more cooling water passing through your engine! Where some confusion may lie is that the indicator is not the only source for cooling water to exit the block....far from it! The majority of cooling water exits at the base of the powerhead where you cannot see it.
> ...



I completely agree with everything you say. When I first took the thermostat out I didn't realize it was stuck in the open position until I had the new one to compare it to. I did not check the actual operating temperature but i can tell you it was running very hot to the touch. After all the work was completed the engine is running much cooler to the touch, you can actually leave your hand on top on the motor while it is running now. I know that's not a good test but I never thought to try and measure the actual temperature. I wish I would have taken some pictures of all of the corrosion in the water passages before i cleaned them out to show how bad things were. 

At least for now it is running very smooth and has a strong exiting water stream. Thanks again for all of the information and help you and everyone else provided.


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