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08-12-2010, 10:15 PM
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#1
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Registered User
Country: Poland
Location: Warsaw
Join Date: Dec 2005
Location: Warsaw
Posts: 580
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Propellers again
Hi Guys,
I was wondering if any of you could help me with finding (teoreticlly) what prop should I use.
Boat:
23 ft deep V twin step around 900 kg with engine and fuel (madness marine sr-23)
Engines, props, speeds, rpm so far:
MERC XR2 Racing, 24x14 3 blade E.T. 5900rpm 103km/h (1,87 CLE)
MERC XR2 Racing, 24x14 1/4 Chopper 5600rpm 98km/h (1,87 CLE)
Yamaha 200Pro V with modified heads (around 210 hp )
24x14 1/4 Chopper 6300rpm 109km/h (1.85 gear box )
25x15 Fury 5400rpm 104 km/h (1.85 gear box)
23x13 3/4 Laser II 6100rpm 106km/h (1,85 gear box)
I will repower my boat with Evinrude 250 H.O. with 1,71 gearbox, max rpm is 6000
What do you think? What prop should I start to test with? My biggest prop is 25x15 Fury but propably it will be too small
I prefer over hub props, I really love choppers. I was thinking about 26x14 or 28x14 but honestly I don't know if 28 would be to big.
Can someone help? Is there any way to calculate it ??
Mike
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08-12-2010, 10:23 PM
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#2
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Registered User
Country: Poland
Location: Warsaw
Join Date: Dec 2005
Location: Warsaw
Posts: 580
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Most important...
I'm looking for good top end
So I don't think that 4 blade prop would be good idea
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08-12-2010, 10:33 PM
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#3
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Senior Member
Country: UK
Location: Devon
Occupation: Garage Proprietor
Interests: PowerBoat Racing
Boat name: If Only
Boat make: Bernico F3 OCR, Bernico Prototype Inboard, and some Ribs
Engines: Yamaha Pro V 115
Cruising area: UK, France
Join Date: Jan 2005
Location: Devon
Posts: 3,095
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PM me your email address and i will send you a Excel file prop slip calculator !!
Bob
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If Only
National Outboard Immersed Propeller Mono Record 103mph
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08-12-2010, 10:35 PM
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#4
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Registered User
Country: Poland
Location: Warsaw
Join Date: Dec 2005
Location: Warsaw
Posts: 580
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PM sent
Thanks
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08-12-2010, 10:49 PM
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#5
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Registered User
Country: UK
Location: Weston Super Mare
Occupation: Electrical Engineer
Join Date: Mar 2004
Location: Weston Super Mare
Posts: 6,351
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in my experience evinrudes need to run deep so you wont want a surface piercing prop. our 250HO on a heavy 21ft boat ran 78mph with a 25 trophy 4 blade and that was the fastest prop of about 10 we tried.
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09-12-2010, 08:41 AM
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#6
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Registered User
Country: Poland
Location: Warsaw
Join Date: Dec 2005
Location: Warsaw
Posts: 580
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Quote:
Originally Posted by Burty
in my experience evinrudes need to run deep so you wont want a surface piercing prop. our 250HO on a heavy 21ft boat ran 78mph with a 25 trophy 4 blade and that was the fastest prop of about 10 we tried.
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4 blade... what kind of boat it was?
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09-12-2010, 06:19 PM
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#7
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Registered User
Country: UK
Location: Weston Super Mare
Occupation: Electrical Engineer
Join Date: Mar 2004
Location: Weston Super Mare
Posts: 6,351
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700xs, the new Gav design, I believe the cyclones also run 4 bladers on there 250HO's
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09-12-2010, 08:08 PM
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#8
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Registered User
Country: Poland
Location: Warsaw
Join Date: Dec 2005
Location: Warsaw
Posts: 580
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Hard to believe that 4 blader is faster than 3 blader in quite light hulls
I'm saying light couse it is not 23ft US Bowrider
What about Fury or Tempest ? Any experience with that props?
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09-12-2010, 09:16 PM
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#9
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Registered User
Country: UK
Location: Weston Super Mare
Occupation: Electrical Engineer
Join Date: Mar 2004
Location: Weston Super Mare
Posts: 6,351
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no mate, we tried, lasers, rakers, et lightening, choppers, trophies and a bravo 1.
maybe its the gearcase design??? i know someone that went from a 280 to a 250HO and he had to drop the motor 3" to get the same sort of bowlift and performance
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10-12-2010, 07:23 AM
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#10
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Registered User
Country: Poland
Location: Warsaw
Join Date: Dec 2005
Location: Warsaw
Posts: 580
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allrhight mate
So I will start with 25trophy :-)
Cheers
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10-12-2010, 07:26 AM
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#11
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Registered User
Country: UK
Location: Weston Super Mare
Occupation: Electrical Engineer
Join Date: Mar 2004
Location: Weston Super Mare
Posts: 6,351
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none of these boats were stepped though, maybe try sending Adam a pm as he ran a 250HO on a 23ft stepped hull
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10-12-2010, 07:28 AM
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#12
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Registered User
Country: Poland
Location: Warsaw
Join Date: Dec 2005
Location: Warsaw
Posts: 580
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that is also good idea
thanks
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10-12-2010, 08:16 AM
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#13
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... sundowner anyone ?
Country: mauritius
Location: flic en flac
Boat make: some rings & phantoms
Engines: some mercs
Cruising area: indian ocean
Join Date: Nov 2007
Location: flic en flac
Posts: 379
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Quote:
Originally Posted by Mike_G
MERC XR2 Racing, 24x14 3 blade E.T. 5900rpm 103km/h (1,87 CLE)
MERC XR2 Racing, 24x14 1/4 Chopper 5600rpm 98km/h (1,87 CLE)
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... which engine height ?
... fueltank at bow or back ?
... xr2 must rev 7000+ for max hp
__________________
regards
chris
bling never made anything fast
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10-12-2010, 08:43 AM
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#14
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Registered User
Country: Poland
Location: Warsaw
Join Date: Dec 2005
Location: Warsaw
Posts: 580
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prop shaft is about 1,5 inch below bottom line
fuel tank at back of the boat
Never seen over 6400 rpm even on my old ring 20C even after rebuilding the engine
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10-12-2010, 08:54 AM
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#15
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Registered User
Join Date: Aug 2009
Posts: 25
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This might help
We have been testing Adam Younger 24ft Batboat with 250xs. Various engine heights and various boat weights due to our class restrictions. Results are as follows.......
Lowest engine height (boat 950kg)
Bravo 1 28 5400 76.5 mph
ET Lightning 28 5700 79.6mph
Tempest 27 5900 82 mph
Height plus 1 inch (950kg)
High 5 25 6200 72mph
Tempest 27 6000 83mph
Bravo 1 28 5600 78mph
Height plus 3 inch (950kg)
Tempest 27 6500 87.7mph
Height plus 1 inch (1050kg)
Bravo 1 26 6100 78mph
Tempest 27 6000 82mph
Great speed from high engine setting but real lousy handling, turning not recommended.
We have decided best race set up is Tempest 27 at plus 1 inch for flat race and Bravo 26 for rough race. Boat handles much better with 4 blades rather than 3. adding 100kg of lead at pivot point in keel makes the boat handle like a dream.
Hope this helps
Cheers Paul
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10-12-2010, 08:59 AM
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#16
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Registered User
Country: Poland
Location: Warsaw
Join Date: Dec 2005
Location: Warsaw
Posts: 580
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So basicly Tempest was the fastest one.
But it is 250XS so propably sport master
and 250H.O. will not run over 6000 rpm
Still thanks for help
Any advice apprciated
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28-01-2011, 06:47 AM
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#17
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Registered User
Location: West Coast of Norway
Occupation: naval architect
Interests: surface piercing props, stepped hulls, air entrapment hulls
Boat name: none
Boat make: PetterTintorera
Engines: Yamaha 90
Cruising area: West Coast of Norway
Join Date: Sep 2005
Location: West Coast of Norway
Posts: 888
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Quote:
Originally Posted by Paul Howes
This might help
We have been testing Adam Younger 24ft Batboat with 250xs. Various engine heights and various boat weights due to our class restrictions. Results are as follows.......
Lowest engine height (boat 950kg)
Bravo 1 28 5400 76.5 mph
ET Lightning 28 5700 79.6mph
Tempest 27 5900 82 mph
Height plus 1 inch (950kg)
High 5 25 6200 72mph
Tempest 27 6000 83mph
Bravo 1 28 5600 78mph
Height plus 3 inch (950kg)
Tempest 27 6500 87.7mph
Height plus 1 inch (1050kg)
Bravo 1 26 6100 78mph
Tempest 27 6000 82mph
Great speed from high engine setting but real lousy handling, turning not recommended.
We have decided best race set up is Tempest 27 at plus 1 inch for flat race and Bravo 26 for rough race. Boat handles much better with 4 blades rather than 3. adding 100kg of lead at pivot point in keel makes the boat handle like a dream.
Hope this helps
Cheers Paul
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What was the hight of the propeller shaft in relation to the keel at the lowest setting?
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