High revs, low thrust

TheBaum

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Water Crafts
2000 RX PWC and 2006 Islandia
#1
I have a 2006 Sea Doo Islandia. Two of the non-SC 4-tec engines.

At idle/low throttle, all is normal. Getting the minimal thrust from both pumps.

At higher throttle, the port engine revs very high and yet no real change in thrust. Starboard engine/pump is performing fine.

Hav searched and read the forums here. I don't have anything stuck in the impeller, etc. etc.

It just started happeninthe last time I drove it... although the boat sat in fresh-water for about a month (with no use.) I didn't hit any logs or sticks or rocks during the prior outing.

Attach is a picture of the impeller. Very minor damage to it. Boat has only about 60 hours total on it.

So, IGNORING ALL THE OTHER possibilities of what could be causing it: Could THAT SMALL amount of damage ALONE cause such a major loss in propulsion?
 

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TheBaum

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Water Crafts
2000 RX PWC and 2006 Islandia
#2
BTW, the splines seem fine (I can't turn the shaft or impeller) and I get some thrust at idle/low throttle.

and engine mounts are fine.

No water leaking into hull.
 

etemplet

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#3
I had a couple of wear rings fail and leave the white part in there. :) Check your wear ring clearance on that impeller housing. Feeler gauge. :) Would be good to compare the clearance on both so you make a good decision.
 

JPass

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2012 Challenger 210 SE
#5
Pull the pump and remove the impeller and rear cone. Inspect how bearings in pump feel when you spin by hand. Make sure no water in the cone or pump bearings.

make sure buckets are moving up and down the same. One could be hanging up a bit.

Shouldn't take more than 20 minutes to remove the pump and start looking a bit deeper.
 

TheBaum

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Water Crafts
2000 RX PWC and 2006 Islandia
#6
Yep, I will definitely have to look at various things.

But, my main question is: (IGNORING ALL THE OTHER possibilities of what could be causing it) : Could THAT SMALL amount of damage on the impeller ALONE cause such a major loss in propulsion?

sure, it would cause the pump/impeller to work less efficiently.. but it couldn't possibly caused thaaaat much cavitation and loss of thrust.. could it?

. I mean, if that little damage caused that much change in propulsion, then people would be replacing impellers each 20 hours of use. ;)


Changing out the impeller is not the most expensive repair job.. but I see no reason to do it if this isn't possibly the cause of the lack of thrust.

...again, the port engine revs very high, but no increase in thrust. other engine is normal rpm with normal thrust at (of course) the same throttle input from the stick.
 
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etemplet

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1996 SPI, 1996 GTX, 1997 GTX
#7
Nope, it is something else. While you have the prop off.... take a hammer to it and a nice heavy flat plate and restore the shape as much as you can. I beat one of mine straight and took the die grinder to it with a carbide tool. Looking at this picture you can imagine the impeller being a bit dinged up.
No affect at all on performance before or after I cleaned it all up. SPI Venturi Damage.jpg
 

mikidymac

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#8
A leaking driveshaft seal will allow air to be sucked from the engine compartment into the pump causing lack of thrust.

Most common cause of your issue is, 1. Bad wearing. 2. Driveshaft seal assuming impeller and driveshaft is good.
 
Messages
17
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Water Crafts
2000 RX PWC and 2006 Islandia
#9
Most common cause of your issue is, 1. Bad wearing. 2. Driveshaft seal assuming impeller and driveshaft is good.
Hi mikidymac, when you say "bad wearing", On which part/component do you mean?

maybe you meant "wear ring" ?

From my photo above, my wear ring does not seem too bad, does it? .. haha, idk, but, I assume everyone's wear ring looks similar to mine after a few hours of boating.
 
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JPass

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#10
Hi mikidymac, when you say "bad wearing", On which part/component do you mean?

maybe you meant "wear ring" ?

From my photo above, my wear ring does not seem too bad, does it? .. haha, idk, but, I assume everyone's wear ring looks similar to mine after a few hours of boating.
There's a maximum acceptable gap between the wear ring and impeller blade. It's kinda hard to say yours is good with a simple picture. When you remove the pump, you can check the gap with a feeler gauge.
 

etemplet

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#11
Hmmmm when you said your wear ring was good I assumed you knew it was good. Get in there with a feeler gauge and check. The white color confused me as it looks like what happens when the rubber component of the wear ring fails and the fiberglass section is showing. I like about .020" on my wear rings. I'm shooting from the hip here but I believe .040" is max clearance. Keep it TIGHT. :D
 

etemplet

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1996 SPI, 1996 GTX, 1997 GTX
#12
The previous owner of this ski I bought a couple weeks ago had some "High Revv No Thrust" issues for sure. I'm debating on what to do with the prop. Believe it or not the impeller shaft is undamaged. 56532051612__1061344A-C2B0-4A39-B02C-BF92EE95B4D6.JPG
 

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