1986 Yamaha 6hp wont pump water without first blowing compressed air throw tell tale

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samuelh1987

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Location
Somerset, KY
LOCATION
Somerset, KY
I'm having a weird issue with a 1986 6hp yamaha. It will not pump water out the tell tale unless you blow compressed air backwards through the system. After doing that it pumps fantastic and will continue to pump after shutting down the engine. If it sits for a day or 2 you have to repeat the entire process. It has a brand new Thermostat and impeller.
 
I have to ask, did you pay attention to the orientation of the vanes of the old pump? Sounds to me like the new one was put in backwards.
 
A piece if old impeller or other debris might be loose inside the powerhead that works its way to the pisser then falls down during the blowing process. Most rubber water pump impellers will self direct after the first pull of the starter rope.
 
Agreed, it sounds like there's a piece of debris acting as a check valve going to the tell - there is hardly any pressure at all at the tell, so it wouldn't take much to block flow to it off.
 
I was thinking debris may be acting like a check valve. I'll pull the lower unit and hit it with the compressor again. Impeller is properly oriented. The motor sat for a few years in a garage before I found it on Craigslist. It starts first pull, and runs great; minus, the water pump issue.
 
I have had this happen on a 25ESH. Customer taught me about it, sometimes that's how you learn things. On that particular motor, the impeller had failed and pieces had gotten jammed up into the water tube. I got all that out no problem, replaced impeller, it pee'd and I was good with that. BUT...Mr. Customer knew that it wasn't peeing as hard as it did new (and all the water pump parts were just that, new) and he bought it back to me a couple times complaining. I was sick of seeing him honestly. So he asked me if it had a thermostat (and it does), asked me to remove it. By now I'm about to get mad, but decided to keep my cool...because it's possible that he "might" be right (though in my mind at the time, "not likely"). Remove 2 bolts, removed thermostat, yep there's a piece of the impeller, stuck in the passage. Reinstalled, fired it up, pees like a brand new motor again. We both learned something, albeit in my case embarrassing.

Since then every single impeller I replace if any of the vanes are missing, FIND them and count them. Should add up to 6 every time. There's been times when a little motor like a 8 or 9.9 I can't find them right off, but removal of the exhaust cover (which has a labyrinth in it) revealed a piece or two. Failure to remove them results in overheating of the exhaust cover and/or the powerhead itself depending on where the pieces are. We obviously don't want that.
 
Thinking it's either lake debris or bugs. The impeller that I took out was in in good shape and still had some spring left. I replaced it be safe. Thermostat was a mess on the other hand.
 
Do believe I got it sorted. Took out thermostat and forced air through all the passages then flushed the head with the water hose.
 

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