help with best impeller for my project

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bagsworth

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« on: May 13, 2018, 01:59:26 PM »
When serving USCG boating safety team in '68, '69, we would work the River between Laughlin and Havasu and there I fell in love with the Jet Boats...  Now 50 years later I finally own one...  While escaping the Montana winter at Pirate Cove I bought a 1968 Hallett 18' that others made few changes over the years, with exception of the pump...  Now has a 454 BBC and the engine runs sweet, the pump is not only worn out but still has a "B" impeller...  We look forward to cruising the river next several years and I just removed the pump and am about to order rebuild kit and am asking for experienced Jet Boat owners to suggest correct impeller...  My goal is to cruise 35 to 40 MPH at 2800 - 3000 RPM ...  My guess is the engine is at 300 HP and we will be two person boat and never plan on using to pull anyone out of the water, unless by throwing them a flotation device :-)   Looking at charts, looks like I should get an "A"  or  "AA" impeller...  Any input appreciated,  Thanks in advance,  bagsworth


Reed2017

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« Reply #1 on: May 13, 2018, 05:19:01 PM »
We all love old Hallett boat pics!


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GT Jets

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« Reply #2 on: May 13, 2018, 09:22:01 PM »
When serving USCG boating safety team in '68, '69, we would work the River between Laughlin and Havasu and there I fell in love with the Jet Boats...  Now 50 years later I finally own one...  While escaping the Montana winter at Pirate Cove I bought a 1968 Hallett 18' that others made few changes over the years, with exception of the pump...  Now has a 454 BBC and the engine runs sweet, the pump is not only worn out but still has a "B" impeller...  We look forward to cruising the river next several years and I just removed the pump and am about to order rebuild kit and am asking for experienced Jet Boat owners to suggest correct impeller...  My goal is to cruise 35 to 40 MPH at 2800 - 3000 RPM ...  My guess is the engine is at 300 HP and we will be two person boat and never plan on using to pull anyone out of the water, unless by throwing them a flotation device :-)   Looking at charts, looks like I should get an "A"  or  "AA" impeller...  Any input appreciated,  Thanks in advance,  bagsworth


Two things to take into consideration.

The first thing is the engine may need some RPM to make some HP, so you can drop it out of a decent curve real quick. I personally would go with an A cut. If you want a decent cruise speed at 3000 RPM, build a v drive.

A double A will simply pull more HP from the engine, it wont necessarily make it any faster at the same RPM as an A, if it did, it will be very slight (maybe 2 or 3 MPH).

Wish I had better news. You will be in the 3,500 to 4,000 RPM to see a decent cruise speed (thinking you are talking 35-40 MPH)..

Good luck and thank you for your service sir. If I may, what part of Montana? I spent some time with my dad and his high school buddy in Trout Creek/Mazula area and was in awe...

GT
  • Boat #1: 1992 Carrera 20.5 Elite (I/O bitches)
  • Boat #2: 19' Bubble deck Jet BBC Berkeley
If i get some free time tonight at work, ill play with it and post it for everyone to see.

Time to man up and yank it John!  :banghead:
Ray

mash on it

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« Reply #3 on: May 14, 2018, 11:48:45 AM »
I noticed a ~200 rpm decrease going from a Berkeley 2A impeller to an American Turbine AA. The AA is bigger than the Berkeley 2A. The difference is partly due to a worn pump. Now at 3K rpm, I'm about 32-ish mph. That's also on a big azz 21' Eliminator Day Cruiser.
On a lil 18 footer, your cruise speeds would likely be higher. (less weight)
However, I prefer 'over' impellering a jet and then adding more horsepower when/if needed.
Just my $0.02

Dan'l
CJ/RR 212...under construction  "Pistol Annie"

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« Reply #4 on: May 14, 2018, 09:39:27 PM »
Congratulations on the purchase.  That is one of my all time favorite hulls. X2 on the pictures.

Have you  driven the boat already?  Do you have any data on various speeds and at what RPM?  To really nail an impeller cut, that info is required.

Just to make sure I understand your specific needs before making a recommendation, please let me know if I missed your point.

The way I understand it is that your primary goal is economy at cruise speed with top speed and hole shot a distant secondary concern.

Normally, what we would recommend for hulls like yours would be a B cut.  That is the best compromise between acceleration and top speed.  It's small enough that it will allow the engine to reach the RPM at which it makes peak power, yet big enough that it still provides a good hole shot.

As GT, my esteemed colleague, pointed out, cruise economy of jet boats is less than stellar.  With that being said, what I would do to maximize cruise economy is go with an aluminium AA or maybe an A+ impeller.  A larger impeller can always be cut down if you need more RPM.

As far as the brand impeller, American Turbine is top quality or get a Heritage from Place Diverter.  Both offer service parts.

All of this assumes proper clearances.  Regardless of which impeller, a properly detailed impeller will make it "bite" harder and ultimately work more efficient.  A detailed bowl will also help the pump work more efficiently.  Less cavitation translates into more thrust.

Some other suggestions to optimize your boat.  I would pass on an inducer.  I would ditch the rock grate for a loader.  If a shoe and ride plate are in the (off-season) budget, I would suggest a back-cut shoe with a 13.5" opening and the biting edge ~1/16" above keel.  A Place Diverter will help you optimize your trim.

Good luck,

Joe
"I want to roll with my brother Joe" - Joe Bateman - January 29, 1950 ~ November 27, 2013

bagsworth

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« Reply #5 on: May 15, 2018, 12:19:41 PM »
Many thanks for the input...  I should have stated how the boat preformed the few times we ran it at the river...  As stated, the 454 BBC runs nice, but I would really have to pay attention to RPM because the pump is so worn?  Using my GPS, at 3500 RPM I was at 22 MPH, and at 5000 RPM I was at 38 MPH.   My goal is to simply cruise at 30 to 35 MPH without running the engine so hard.  Hole shot, or trying to keep up with the big boys is not a concern.  Thanks again for the input.

mash on it

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« Reply #6 on: May 15, 2018, 01:35:50 PM »
Sounds like that pump is toast.

At 4900 rpm, I'm at 57 mph Up river, and down river at 61 or so.

Even my 350/dominator (A impeller) combo would squeeze out 55, in a 19' bowrider (@4600rpm)

Check your tachometer too. Might be off ?

Dan'l
CJ/RR 212...under construction  "Pistol Annie"

Flusher

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« Reply #7 on: May 15, 2018, 04:55:54 PM »
Sounds like more than just wear.  It needs to come apart for inspection.
"I want to roll with my brother Joe" - Joe Bateman - January 29, 1950 ~ November 27, 2013

bagsworth

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« Reply #8 on: May 16, 2018, 05:36:47 AM »
i just pulled the drive apart, waiting for tools to remove the impeller and take it to the next level.  First guess after looking at the impeller, it is a B and appears to be pretty much sand blasted, also the clearance has to be severely worn, I can move the shaft up and down, side to side, pretty sloppy, have not actually measured for clearance.  I plan on doing complete rebuild on the drive, just torn on weather to order A  or  AA impeller.

bagsworth

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« Reply #9 on: May 17, 2018, 09:58:53 AM »
All have talked about "cut"...  As I inspect the impeller, it is marked "B" however I notice the vanes have been ground back, which I assume indicates this has been "cut"...  I called the previous owner and he stated he did not know the history of the boat, but did say the 454 BBC was placed couple owners back...  I tried to insert image of the impeller, no luck...  My guess is with the wear and tear combined with the "cut" is cause for under performance ?   Still waiting on tools to pull the impeller and replace bearing, bushings and seals...  I can email picture of impeller if that helps?   I really do appreciate your input,  with respect, bags

mash on it

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« Reply #10 on: May 17, 2018, 12:02:13 PM »
Sure

PM sent

Dan'l
CJ/RR 212...under construction  "Pistol Annie"

 


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