impeller damage?

[Barry Ceci]

My Scarab 195 (2017) picked up a wood chip that jammed the impeller. When the event occurred It was able to run up to 6 mph at 3000 rpm before pump cavitation but additional rpm produced no additional speed. Put it on the trailer and was able to remove the wood chip through the intake grate.

So,

1. how is it possible for the pump to produce speed up to 5 mph if the impeller is jammed?
2. Is there more than a single impeller in this jet pump?

Barry

 

[Sidarousmg]

the impeller was not likely actually "jammed", it was still able to move but with additional resistance and cavitation that would not allow you to generate thrust or speed (probably created hard vibrations above 3k rpm?). if you have removed the wood chip, put it back in the water and test it, you will likely be back to normal, unless it cause damage to the wear ring, or if there is something else still stuck in the impeller

 

[Barry Ceci]

Thanks Sid,
I'll launch and give it a try.
Barry

 

[bobkeesecker]

Thanks both of you for posting this. Exactly what I needed. Only my second year as a boater, and learning it all with a jet boat. Going out the channel the other day, starboard motor suddenly had rattling noise. Of course it was impeller sucking something in (1/2" branch about a foot long), but I wasn't sure. If I were aware of the reverse thrust procedure, I would have done it. If I were smart enough to turn around right there in the channel and go back in (now I am), I would have. Backed off to neutral right away, noise subsided. Proceeded out into the lake, and as you said, @Sidarousmg, was fine until about 4k rpm when the hard vibrations started. Came back in, looked underneath, discovered the chopped-in-half branch in the impeller, pulled them both out, went back out, same issue at 4k rpm. Noticeable diminished thrust compared to port motor. I'll look underneath when the forklift has it up and post back. Hopefully just another piece in there I missed.

 

[Winerocks]

Likely a piece still in there. It doesn’t take much.

 

[bobkeesecker]

Yup, it was a small piece still in there. "Small" is a relative term. As you said, @Winerocks, "It doesn't take much." Another big lesson learned for me.
By the way, if you can see the outline of the old boat name letters in the background, I buffed them out yesterday with oxidation remover. Not only are the outlines gone, but the original white is also back - along with the light scratches! Looking forward now to doing the rest of the white part of the hull. More learning.