# Yamaha water pump fail - just sharing for sharing



## Smackdaddy53 (Dec 31, 2012)

It only takes a few seconds of losing prime to smoke an impeller and it will blue the liner and melt the nylon just like that. I have a big box full of them from customer’s outboards. That little rectangle hole in the top of the cup is actually dual purpose. It is a locator tab to ensure proper clocking of the cup and it is a vent to allow the pump to maintain prime and not get vapor locked. If that hole gets plugged it will smoke the impeller just like you lost water to the water intakes. 
If we can ever fly again without getting the jab I’ll fly over and fish with you and bring one of my low water pickup systems to install.


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## Paul Mills (Mar 26, 2018)

@Smackdaddy53 I'd go through a couple of impellers a year. I'm always watching the pressure gauge running. It's the bane of my life. I'll probably start looking out for a spare lower unit and think about buying a kit from the US that I can swap out.


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## lemaymiami (Feb 9, 2007)

I won't rig a skiff without a water pressure gauge - they're that important to me... I run a fair amount at night and if you wrap a plastic bag around your lower unit (or load up with grass) it immediately shuts off your water flow to that all important pump. Catch it when it happens, stop and clear it, and you'll never fry that pump.... My water pressure gauge is the only one I keep an eye on when running at night... 

If I found myself suddenly wealthy - NZ is one of the very few places on this earth I'd love to visit and fish... The few folks I've met from there years ago were super...


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## Paul Mills (Mar 26, 2018)

Well the drama hasn't ended with this event juuuuust yet. Replaced the pump for a new built up one. Checked the thermostat in boiling water and its working as it should, had a look at the poppet valve and assembled al that end. 

Put muffs on and water and I dont have any water coming out of the pee pipe running. Tried running with lower unit submerged in my wash drum and still no pee.

Striped the pump back down and put it back together, still nothing. 

With the lower unit off forced water up the water intake pipe with the hose, water comes out both the thermostat housing (with cover off) and pee pipe. So I'm pretty sure no blockage there.

Put her all back together and no matter what I try, the water pump wont get water to the powerhead. Be good to be able to test the lower unit and pump while I have it off but the shaft is too large for the chuck in my drill so I can spin it. 

Really bizzare. Never struck this one. Heaven forbid I call a mechanic but its getting close.


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## mwolaver (Feb 6, 2014)

Paul Mills said:


> Well the drama hasn't ended with this event juuuuust yet. Replaced the pump for a new built up one. Checked the thermostat in boiling water and its working as it should, had a look at the poppet valve and assembled al that end.
> 
> Put muffs on and water and I dont have any water coming out of the pee pipe running. Tried running with lower unit submerged in my wash drum and still no pee.
> 
> ...


Can I assume that you have used the muffs on this motor before? I cannot run my 40 that way, is why I ask. Trying to remember...thought my 90/2 stroke had a flush fitting also? Another stupid question: you put the woodruff key back in, yes?


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## Paul Mills (Mar 26, 2018)

Key is def back in.

It has a flush intake and it pee's when I hook that up. It pee's when I put a hose direct onto the bottom of the water intake pipe that leads to the powerhead.

I just ran the lower unit down to a local Yamaha mechanic. He is flat out bust but had a look at my work. He is stumped (that is from what he saw and what I told him, I didn't take the boat down just the lower unit).

He did suggest drop it in the water and see if it runs with the lower unit more "submersed". That seems a bit desperate as I've never had this before, ever. It has always run in the past on the muff or in the flush tank. Flush tank covers the cav plate, just.

I am reaching out to a mobile mechanic who can hopefully come to my house and take a look. The only other place water can escape in my view is where the water intake pipe enters the powerhead. I cant see that easily however and I cant even imagine why that would come loose or fail.

Weird.


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## Smackdaddy53 (Dec 31, 2012)

Is the water tube mating up with the water pump correctly?


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## Paul Mills (Mar 26, 2018)

@Smackdaddy53 yup.

I found the problem. Just went back to basics and concentrated on the pump. 

Ran it without the thermostat and poppet valve and cover off. No water.

So I rebuilt the pump using a used impeller. Bingo, the bugger started peeing.

What I did notice is that the so-called "new" impeller doesnt have a brass bushing inside. I could make out marks on the inside of it where it appears to be spinning on the wood drift key. I'll post a pic. First time Ive ever had that and I cant find the packaging to question whether it is an authentic Yamaha part.

So my question is: Do genuine impellers have a brass bushing insert?

I would love to do away with this pump system altogether. It's a weakness in outboards that run shallow. I run my skiff in 1ft of juice some days. Also the dang sea grass after a storm can sit in big mats on the surface, its tougher than it looks!

Thanks for the input team.


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## Smackdaddy53 (Dec 31, 2012)

No, the Yamaha 90TLR impeller has no brass inner bushing. There are a lot of counterfeit parts on the market that even have imposter packaging.
My pickup system would cure your issues and your water pump would last many times longer with it. My pump is perfect and it’s almost 4 years old along with my pickup system from the first day I tested the prototype. It’s on a 70TLRZ.


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## Paul Mills (Mar 26, 2018)

Here is a picture of the "new" impeller I installed after I had the overheat.










You can see the issue. The key way for wood drift key has failed in a way. I thought when I put this one on that it slipped onto the drive shaft way to easily (usually they are a good press fit). It also felt like a softer rubber than my others.

Wasnt until I tried an older used impeller that I really noticed this. The used impeller has got the pee pipe going, not strong like a 100am morning pee but it is going enough at idle to run.

I've ordered another impeller. A genuine Yamaha one.

Happy to share. This is thee first time I have struck this. Lesson here is, believe you gut and go back to basics. Always had to be the water pump, couldn't be anything else after all the fault finding I did.


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## Smackdaddy53 (Dec 31, 2012)

Check your messages.


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## MT_Flyfisher (Sep 2, 2021)

Thanks for posting, helpful!


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