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Discussion Starter · #1 ·
I changed out my water pump and thermostat on my 2008 yamaha 25 2-stroke, and now I have no water flow discharging from the motor.

I know I'm getting water to the thermostat, I just don't know if I'm getting water through the thermostat or if it's getting blocked somewhere else. I have no clue what the flow path looks like downstream of the thermostat...is there anything I can check to find the problem?

Is it common to install a new thermostat and it just not lift or let flow by for some reason? I ordered the part from boats.net and just dropped it in the slot and bolted the cover back on.

Thanks for the help!
 

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How do you know your getting water to the thermostat? Pull the thermostat out and out it in some boiling water and see if it opens.

You might be pumping some water to get to the thermostat but might not have enough pressure to actually pump water through the entire system.

Did you replace the housing, when you did the water pump? If it worked before you changed it then you got something wrong somewhere.

Are you running it on a house or in the water?

A little more info needed.

Creek standing by.
 

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Discussion Starter · #3 ·
I know I'm getting water to the thermostat because I pulled it and cranked the motor with the thermostat  cover off long enough to see water come pouring out.   

I did the water pump at the same time.  I didn't change the water pump housing because it still looked brand new. I do the water pump every year.  My first time with the thermostat. Seemed pretty fool-proof when I was doing it, but I may have it wrong.

Ran it on the hose and on the water. Same result.
 

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I know I'm getting water to the thermostat because I pulled it and cranked the motor with the thermostat  cover off long enough to see water come pouring out.   

I did the water pump at the same time.  I didn't change the water pump housing because it still looked brand new. I do the water pump every year.  My first time with the thermostat. Seemed pretty fool-proof when I was doing it, but I may have it wrong.

Ran it on the hose and on the water. Same result.
Put the thermostat in some boiling water to make sure its opening, are you sure you let the engine run long enough to come all the way up to temp and the thermostat to open?

If your letting it run long enough to get up to temp, and the thermostat does open, then your losing pressure. I would guess the water pump housing is sucking air, also replace the water tube bushing.
 

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Thermostat is pretty fool proof only goes in 1 way, if your able to do the impeller than the thermostat is simple.
 

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Discussion Starter · #6 ·
Thanks for the input.

I'll pull it tomorrow and put it in boiling water tomorrow. If it opens, I'll put a new housing and bushing on.

I ran it for a couple of minutes. I kept my hand on the block to make sure it didn't get too hot, but it definitely got warm. It usually starts "peeing" within a few seconds.
 

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Okay so it's either

1) you just didnt run the engine long enough to get it up to temp 170 degrees for the thermostat to open. I would run the engine again and you can put a temp on it.

2) Boats.net might have sent you the wrong thermostat, check the packaging with the number you ordered, that motor might take a lower temp thermostat. I'm not able to get on Yamaha website to check the manual on your engine right now. You could probably find it online though, if not on Monday I can look up the specs for you.

3) You are sucking air somewhere and losing pressure, most likely the W/P housing.

Creek
 

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Discussion Starter · #9 ·
An update.

Replaced the housing and water bushing...nothing.

Back flushed water tube from the thermostat housing...nothing.

Scratched my head for a while, then stuck a paper clip up the discharge hole to make sure it was clear. Got a bubble of mud then here came the water. Got full pressure after a few minutes of running.

Someone please come take my engineering degree from me, haha. Thanks for the advice!
 

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Didn't you day it was overheating?
A mud dobber in the tell tail hole won't cause an overheat
 

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Discussion Starter · #11 ·
Not overheating. Just no flow out of tell tale. Just thought it was a thermostat problem since I knew I was getting water to it, was unsure if the water was getting past it.
 

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Big difference between not pissing out of the tale tale, than not discharging water out of the motor.

Sorry for making you spend the bucks on the W/P housing.
 

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An update.

Replaced the housing and water bushing...nothing.

Back flushed water tube from the thermostat housing...nothing.

Scratched my head for a while, then stuck a paper clip up the discharge hole to make sure it was clear. Got a bubble of mud then here came the water. Got full pressure after a few minutes of running.

Someone please come take my engineering degree from me, haha. Thanks for the advice!
Been there, done that. Don't feel bad.
 
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