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Ryan
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171 Posts
Discussion Starter #1
Launched at Jack Smith on Friday and was cruising down river when the boat started cavitating and seemed to have lost power. Motor was still turning RPMs but could not do much more than idle. Wasnt sure what it was but thought it might have been something stuck in the impeller. Took the boat to the beach and took off the inspection plate but couldnt find anything while out on the water. Idled about 45 mintues back to the ramp and when on the trailer was able to find and pull out the stick.

Question:
My logic tells me that because the shaft was still turning and the impeller was not that I could have caused damaged by running the boat back to the ramp.
Has anyone had a similar experience and what do you guys think could have been done to the pump by doing this? Took the boat back out and seemed to be running ok but with a full load of people and gear seemed to lack the hole punch that it usually has (or Im just being paranoid).
No play in the shaft, anything else that I should check?

Thanks
 

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Registered
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If you spun the impellor on the shaft there is no way that you would run OK with a full load. If the stick was blocking any water from getting through the impellor it will cause the cavitation
 

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Ryan
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171 Posts
Discussion Starter #3
I know that the stick caused the cavitation, Im trying to figure out if you can damgae the pump by running the boat while there is something stuck in the impeller. :)
 

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Premium Member
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70 Posts
Ultra,
Years ago I had a similar experience but it was a plastic bag. I had to cross Havasu with the boat cavitating. In my case it obviously did not damage the pump, but what I was unaware of was, that a temperature gauge does not work if there is no water in the block. The boat did not show anything on the temp gauge but cracked the block in several places and and blew both Head gaskets. Another expensive lesson learned.

My Boat was a CP and the only way to remove anything from the pump was to put it on a trailer and back it off a curb so I could fit under it.

I am sure that in your case the wooden stick only disrupted the flow to the impeller, and did not damage anything. You probably should check the edges of the impeller, but if it is like my cruiser it it is difficult to see or feel anything without removing the grate.
 

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I've gotten stuff stuck in my impeller a few times,

I've found getting on plane and letting off will sometimes suck it out,

or get a couple buddies on the bow, and get the jet up on a beach so you can go into the hand hole,

no reason for something in the jet to ruin your day,

your engine is putting a lot more load on the impeller then a small stick could,

I'd guess you had a problem before if your impeller is free wheeling on the shaft
 

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Ryan
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171 Posts
Discussion Starter #7
I was concerned about water getting to the block and the temp so I was watching that along with the oil pressure the entire trip back up river and both were good, temp stayed at 125 the entire time.

Just to clarify, the impeller is not moving freely on the shaft, I could see the shaft rotating but the impeller was not moving because of the stick.

I was thinking that it may have caused stress to the pump thus causing internal damage but Im just guessing as I dont know a lot about the internal workings of the pump.

Appreciate the feedback.
 

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Sit N' Spin
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1,423 Posts
I was concerned about water getting to the block and the temp so I was watching that along with the oil pressure the entire trip back up river and both were good, temp stayed at 125 the entire time.

Just to clarify, the impeller is not moving freely on the shaft, I could see the shaft rotating but the impeller was not moving because of the stick.

I was thinking that it may have caused stress to the pump thus causing internal damage but Im just guessing as I dont know a lot about the internal workings of the pump.

Appreciate the feedback.
OK...whats not making sense here is that there is a shaft key that locks the impeller onto the shaft so that it cannot freespin on the shaft. This would mean that is you saw the shaf turning, the impeller should be turning too. If you see the shaft turning yet the impeller is not turning, this means that the shaft key may have been sheared when the stick got into the pump, allowing the shaft to spin freely inside the impeller hub while the stick held the impeller still and kept it from turning.
 

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Ryan
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171 Posts
Discussion Starter #9
OK...whats not making sense here is that there is a shaft key that locks the impeller onto the shaft so that it cannot freespin on the shaft. This would mean that is you saw the shaf turning, the impeller should be turning too. If you see the shaft turning yet the impeller is not turning, this means that the shaft key may have been sheared when the stick got into the pump, allowing the shaft to spin freely inside the impeller hub while the stick held the impeller still and kept it from turning.

So if the shaft key was sheared, i would be able to move the impeller by hand, correct? This is not the case, I could not move the impeller by hand. But while the stick was in there, I could see the shaft rotating....

Sorry if its confusing
 

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jetboataholic
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2,798 Posts
I doubt that a 3 inch stick could stop the impeller and cause the shaft key to shear off. The impeller is thicker than 3 inches and there is nothing to get caught on in the suction piece, to wedge the stick in such a way that the impeller actually stops turning. But, if it went through the impeller and got stuck on one of the bowl vanes, it might hold up the impeller and cause the key to shear off, but again highly unlikely. If the impeller was free spinning, you would not be able to go anywhere, that shaft would spin inside the impeller, and the impeller would barely move. Also, if you sheared that key, you would have heard a terrible racket coming from your pump, and to do this that stick would have to hold up the motor too, meaning that the shaft would not be turning for a bit and your motor would be making all kinds of racket and it would likely hurt it too because jet pumps are a direct connect, there is no gearbox or neutral. So if the pump stops, then the motor stops and visa versa. Understand?

:)hand
 

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Sit N' Spin
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1,423 Posts
So if the shaft key was sheared, i would be able to move the impeller by hand, correct? This is not the case, I could not move the impeller by hand. But while the stick was in there, I could see the shaft rotating....

Sorry if its confusing

If the shaft is rotating the impeller is rotating too because the key locks the impeller to the shaft so that it turns with the shaft. Unless that key is either sheared or missing, there is no possible way for the pump shaft to turn without the impeller turning as well.
 

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jetboataholic
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The shaft should not turn unless the impeller turns. If one turns and the other does not, you have a problem. You may want to take another look at what is going on in there and you may have sheared off the key and if it turned too much may have dammaged the impeller and the shaft. Check and see if the impeller is turning free of the shaft.

Cy
 

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several times I have just dunked under water and stuck my hand up the intake and pulled out stuff. rocks, stick, plastic bags, ski ropes, ropes are:|err bad because you need a knife.
 

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Ryan
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171 Posts
Discussion Starter #16
I doubt that a 3 inch stick could stop the impeller and cause the shaft key to shear off. The impeller is thicker than 3 inches and there is nothing to get caught on in the suction piece, to wedge the stick in such a way that the impeller actually stops turning. But, if it went through the impeller and got stuck on one of the bowl vanes, it might hold up the impeller and cause the key to shear off, but again highly unlikely. If the impeller was free spinning, you would not be able to go anywhere, that shaft would spin inside the impeller, and the impeller would barely move. Also, if you sheared that key, you would have heard a terrible racket coming from your pump, and to do this that stick would have to hold up the motor too, meaning that the shaft would not be turning for a bit and your motor would be making all kinds of racket and it would likely hurt it too because jet pumps are a direct connect, there is no gearbox or neutral. So if the pump stops, then the motor stops and visa versa. Understand?

:)hand

I understand, thats why I was confused. Can you explain to me what was happening in there when the stick was lodged in there, Im trying to understand what happens in there.
All I know is that I got under the boat, looked at the impeller and it was moving once I took the stick out and then the boat ran like normal. The stick was obviously lodged in the impeller and not allowing it to move, right?
There was no loud racket or anything of that nature, just some vibration when the stick initally got stuck.
 
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I understand, thats why I was confused. Can you explain to me what was happening in there when the stick was lodged in there, Im trying to understand what happens in there.
All I know is that I got under the boat, looked at the impeller and it was moving once I took the stick out and then the boat ran like normal. The stick was obviously lodged in the impeller and not allowing it to move, right?
There was no loud racket or anything of that nature, just some vibration when the stick initally got stuck.
No, the impeller was turning fine. The stick caused "cavitation" which makes the boat feel like it's in neutral or strained. The stick didn't cause the impeller not to turn, it caused it to cavitate.
 

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jetboataholic
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2,798 Posts
I understand, thats why I was confused. Can you explain to me what was happening in there when the stick was lodged in there, Im trying to understand what happens in there.
All I know is that I got under the boat, looked at the impeller and it was moving once I took the stick out and then the boat ran like normal. The stick was obviously lodged in the impeller and not allowing it to move, right?
There was no loud racket or anything of that nature, just some vibration when the stick initally got stuck.
Have you ever rebuilt your pump? Do you know the basic layout, and workings of the pump? A 3" stick cannot stop the impeller from the intake side.

My best guess, would be that the pump was trying to force water through 3 holes, instead of the usual 4 holes in the impeller, causing the cavitaion, thus the vibration. But, I'm no expert on this, hell my boat isn't even running yet. But, I doubt you would be able to make it back to the dock, under power, if the impeller was free spinning on the shaft because you can't get any thrust that way. And the motor wouldn't get any water for the cooling system, so you wouldn't be running at 125*.

Good luck.
 

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jetboataholic
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