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06-07-2005, 09:37 PM
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#1
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Registered User
Country: uk
Location: river tamar
Occupation: self employed
Interests: boats, bikes, bits of other things
Boat name: nothings free
Boat make: cobalt
Cruising area: plymouff
Join Date: Apr 2005
Location: river tamar
Posts: 11
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explain props so I can go faster plse
Okay so i need to gain some speed on my mate.......tried chucking people overboard, removing all kit, even driving near naked but need to know about props.
So a 21 by 14 3/4. or a 21 by 14 1/4 assuming each move 21 inches through the water for every turn and i've got the old girl on full loud and in the rev range, whats the effect of a bigger diameter (the prop!).
Do some props get more of the boat out the water?
What about the make of the prop?
Ive got a Volvo SX leg and a 195 V6. Yep should have got the V8.
Captain Crawfish.
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captain crawfish
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06-07-2005, 11:45 PM
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#2
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Registered User
Country: England
Location: Birmingham
Occupation: Scratching
Interests: Big Dinners
Boat name: Never Enough
Boat make: Seaquel 600xs
Engines: 225hp Merc ProMax
Cruising area: Anywhere! I prefer Weymouth
Join Date: May 2005
Location: Birmingham
Posts: 3,232
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To go faster you need more power rather then a better prop!
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I got jumper cables!
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07-07-2005, 09:15 AM
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#3
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Traveling
Country: UK
Location: Alderholt
Occupation: Aerospace
Boat name: T/T D2S
Boat make: Midas 27' Cat, Argo 16 Cat. Avon Rib Thingy
Engines: Merc 280-ROS -JSRE,65Xs, 75 Stinger, Yam 60
Cruising area: Any Seedy Bar
Join Date: Sep 2004
Location: Alderholt
Posts: 4,225
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Have a look at the link
http://www.mercurymarine.com/everyth...ut_propellers5
that will explain how they work.
you will need to know your gear ratio & RPM to calculate the performance difference, with regard to the dia of the props that will show the difference in the % slip, the calculation on works on pitch only. Bigger dia less slip (in Theory). It is just that
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At least 75% of people who read this will try to lick their elbow!
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07-07-2005, 11:28 AM
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#4
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numbskull
Country: United Kingdom
Location: South
Occupation: none
Interests: none
Boat name: Leviathan
Boat make: Phantom 28
Cruising area: South Coast
Join Date: Mar 2004
Location: South
Posts: 15,959
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If you're within your rev range when flat out, any advantage from props is gonna be small, unless your current prop is badly damaged.
you are already using all your hp, as it's not over revving (or under) and as it's a trimmable drive system, playing with the trim at WOT will make up for most prop types.
What prop is it that you currently run?
I would say, get some more Gee-Gee's if you wanna go quicker.
I'm sure they did a 200+ hp version of the 4.3 V6, find out what the diference is (in engine spec) as it may be pretty simple to upgrade the motors power.
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"I Agree with everything you say really!" - John Cooke to Jon Fuller - 26-01-2013
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07-07-2005, 11:41 AM
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#5
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The Doc
Join Date: Mar 2004
Posts: 8,291
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Quote:
Originally posted by Jon Fuller
[BI'm sure they did a 200+ hp version of the 4.3 V6, find out what the diference is (in engine spec) as it may be pretty simple to upgrade the motors power. [/B]
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Just dont go asking Volvo how to increase HP on a v6 they kinda laugh in your face.
I got some joy with an american custom car co. as thats another yankee block innit?
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07-07-2005, 12:03 PM
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#6
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numbskull
Country: United Kingdom
Location: South
Occupation: none
Interests: none
Boat name: Leviathan
Boat make: Phantom 28
Cruising area: South Coast
Join Date: Mar 2004
Location: South
Posts: 15,959
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you need the microficshe, just compare part No's of stuff like cam, valves, etc.
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"I Agree with everything you say really!" - John Cooke to Jon Fuller - 26-01-2013
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10-07-2005, 02:55 AM
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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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Re: explain props so I can go faster plse
Quote:
Originally posted by willfree
Okay so i need to gain some speed on my mate.......tried chucking people overboard, removing all kit, even driving near naked but need to know about props.
So a 21 by 14 3/4. or a 21 by 14 1/4 assuming each move 21 inches through the water for every turn and i've got the old girl on full loud and in the rev range, whats the effect of a bigger diameter (the prop!).
Do some props get more of the boat out the water?
What about the make of the prop?
Ive got a Volvo SX leg and a 195 V6. Yep should have got the V8.
Captain Crawfish.
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Yes every prop is diferent, get one worked for your need, more bow lift etc etc.
give prop revolutuons a call for more help
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10-07-2005, 09:33 AM
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#8
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Registered User
Country: United kingdom
Location: West Sussex
Occupation: Grease Monkey
Interests: Makin my boat faster!
Boat name: S.B Racing
Boat make: Ocke mannerfelt canopied B23 / Zapcat
Engines: Merc 200XS Gen 2 / Tohatsu 50
Cruising area: littlehampton/Southampton
Join Date: Jan 2005
Location: West Sussex
Posts: 2,656
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Hey burty have you got prop revolutions number?
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Class 3C Mono EPA National speed record holder 95.35 mph Avg!
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10-07-2005, 09:42 AM
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#9
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Registered User
Location: GOLDEN MILE
Boat name: LILY THE PINK AND TERMINATOR 11
Boat make: PHANTOM 21 AND 20
Engines: 2.5 EFI X 2
Join Date: Mar 2004
Location: GOLDEN MILE
Posts: 2,475
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01202 671226
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10-07-2005, 11:00 AM
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#10
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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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Quote:
Originally posted by scottyboy
Hey burty have you got prop revolutions number?
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yup
Quote:
Originally posted by roofer
01202 671226
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11-07-2005, 05:31 PM
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#11
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Registered User
Country: uk
Location: aldershot hants
Occupation: marine engineer
Interests: powerboats carriage driving
Join Date: Jun 2005
Location: aldershot hants
Posts: 14
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you can use a rule of thumb formula, 1" of diameter or pitch will relate to 200-250 revs on your engine. give us a ring on 01252 316412 for more info
regards
Geoff
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