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Jet Pumps / Re: Stainless Impeller = More noise?

« Last post by MPKardell on September 08, 2026, 01:14:57 PM »

The "normal" (but still louder than the aluminum impeller) driveline clatter goes away at about 1000 RPM.  Noise starts to come back at about 2800 RPM.  It's not the loud mechanical clatter that I have at low RPM, but more of a "drone".  Unfortunately, this is in the range of RPM that we cruise at.  The cruise to our favorite skiing cove takes about 40 minutes, which has become a long time for me to endure an annoying sound...

I think the pump/hull combination hits a natural structural frequency of some sort at 2800 RPM.  There has always been drone starting at about 2800 RPM, but it's just so much worse with the stainless impeller.

Also: This has been the case with two completely different engines (Olds and BBC), so I don't think it's an engine balance issue.

Thanks again for you thoughts.

Matt

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Jet Pumps / Re: Stainless Impeller = More noise?

« Last post by mash on it on September 08, 2026, 12:18:17 PM »

Probably sounds like a rattling vibration.
Just add some rpm.
Id much rather have stainless than an aluminum impeller.

Does it go away with the tiniest bit of throttle?

Dan'l

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Jet Pumps / Re: Stainless Impeller = More noise?

« Last post by MPKardell on September 08, 2026, 10:37:43 AM »

Thanks for the reply.  Sounds like it isn't particular to my boat then.  I guess I'm just getting old, but I don't tolerate the noise like I used to.  Looks like I'm going back to aluminum...

Matt

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Jet Pumps / Re: Stainless Impeller = More noise?

« Last post by mash on it on September 08, 2026, 10:02:37 AM »

Mine did the same thing.
Noticably louder.
I bumped the idle up to 900 rpm from 7-750 rpm.
Slightly more load on the impeller made it quiet down.

Just my $0.02

Dan'l

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Jet Pumps / Stainless Impeller = More noise?

« Last post by MPKardell on September 03, 2026, 02:16:31 PM »

It's been a (long) time since I logged in to this site, and things look kinda dead, but I'll give it a shot since there used to be lots of knowledgeable folks here:

I have a 1991 22' Dana day cruiser that I've owned since new.  Bought a bare hull with the fuel tanks and an American Turbine 9.25" pump installed, and then rigged it myself over the course of a year.  I ran an aluminum impeller until I switched out the pump with another 9.25" American Turbine pump that I bought as a "spare" a couple of years ago.  I installed a new stainless 9.25" impeller in the spare pump, along with new bearings and seals.  The idea was that this would be the last pump build that I'd ever have to do...

After the change-over, I had a lot of noise in the pump/driveline/hull.  I then switched back to the old pump to verify it was something to do with the "new" pump, and the "new" noise went away.  The stainless impeller is considerably heavier than the aluminum impeller, so I thought it might need to be balanced.  So I sent the shaft and impeller off to ARS Marine and had them balance it.  After it came back, I put everything back together and clearanced the assembly per standard procedure.  The balanced impeller is better, but still noisier than the aluminum impellers that I've run in the past.

I also rebuilt the driveline, but the old u-joint bearings were still okay (no slop).  The engine is mounted solid to the stringers (no rubber).  I took great care to try and get the pump shaft parallel to the engine centerline, and the offset angle in each u-joint is about 3/4 degree to encourage lubrication of the joints.

This is a closed-bow boat, with the bow open to the cockpit.  We store skis and stuff under the bow for easy access, so I don't really want to close it off.  I have a feeling that the semi-enclosed area in the bow is acting like a horn and amplifying the vibrations being transmitted into the hull from the pump.  But I'm at a loss as to how to reduce the pump vibrations without going back to an aluminum impeller (which I'm ready to do...).  I've bought some sound mat that I plan to install on the underside of the bow deck this fall.

Has anyone experienced something similar when changing from and aluminum impeller to stainless?

Thanks in advance for your input!

Matt

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Boats For Sale / Re: I'm looking to buy a jet !!!!

« Last post by Jnaldrich25 on September 03, 2026, 08:14:52 AM »

I have an ULTRA Custom 20' open bow for sale. Little more than 15K tho....[attachimg=1]

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The No Wake Zone / Re: 2026 One Hot August Night

« Last post by 76Mantra455 on September 02, 2026, 07:10:15 AM »

Jet Boat Show and Shine SCJB

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The No Wake Zone / looking for previous owners

« Last post by jodowii2 on August 25, 2026, 08:36:31 AM »

recently acquired this 78 hallett mini day cruiser, im in Missouri and was told it came from California at some point, California registration CF 8726 GF    and has "you seruous clark??" painted on the back had a decal at one time that said years wages on the sides, (used ai to add it back).[attachimg=1]

but does anyone recognize this boat?

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The No Wake Zone / Re: 2026 One Hot August Night

« Last post by Brad @ SCJB on August 20, 2026, 10:19:26 AM »

Nice! See you there!

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The No Wake Zone / 2026 One Hot August Night

« Last post by 76Mantra455 on August 19, 2026, 05:12:22 PM »

Hey yall ain’t posted in a while been busy working and boating. The Mantra will be there for the event.
https://youtube.com/shorts/1HCERBwLZw4?is=Fp_LW3F2nplw_SeG