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07-11-2004, 07:29 PM
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#1
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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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engine height
whats the optimum engine height for speed in relation to the bottom of the hull if you have a bullet box and a et prop
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07-11-2004, 07:32 PM
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#2
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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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just wondering because if i raise my engine as high as it will go on the power lift the bullet is level with the bottom of the hull. i was just wondering if you would go any faster if it was even higher.
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07-11-2004, 09:22 PM
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#3
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Registered User
Country: US
Location: Virginia
Interests: Quiet desperation
Boat name: A Little Noisy
Boat make: Excalibur 24
Engines: Express Racing 525
Cruising area: Mobjack Bay (where?)
Join Date: Mar 2004
Location: Virginia
Posts: 1,974
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A bullet even with the bottom of the hull results in a surfacing propulsion system.
Experimentation will determine the optimal height. If your gaining revs but not speed, you're too high.
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08-11-2004, 08:59 AM
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#4
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BananaShark Member
Country: UK
Location: Salcombe South Devon
Occupation: Racer and builder
Interests: Winning races
Boat name: BananaShark
Boat make: BananaShark 34' Race
Engines: Twin Yanmar BY 260's
Join Date: Mar 2004
Location: Salcombe South Devon
Posts: 4,638
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And you had better have a water pressure guage!
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Cookee
British Champions! RIB Formula 1 2005
National Speed Record Holder at 90.15 (still)
www.bananasharkracing.com
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08-11-2004, 07:00 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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yep got a water pressure guage.
spent ages reading posts on S + F last night it seems they think that the height for optimum speed is between 1" and 1 1/2" above but i'm worried this may be a little high.
my jack plate has approx 6" of travel so just wondering where you run if its rough?
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08-11-2004, 07:31 PM
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#6
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Registered User
Country: england
Location: Jersey
Occupation: journalist
Interests: Boats
Boat name: Wassup
Boat make: sunseeker
Cruising area: Channel islands
Join Date: Apr 2004
Location: Jersey
Posts: 37
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[so just wondering where you run if its rough? [/B][/QUOTE]
In the container bay
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08-11-2004, 09:55 PM
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#7
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Registered User
Country: Ireland
Location: Dublin
Occupation: Boatbuilder
Boat make: Hydrostream V-king, 650SS OCR ,Ring 21, Ring 18, Phantom 18.
Engines: 300Hp Mercury 2.4, 130 Yamaha, Bridgeport EFI, XR6, Merc 200.
Cruising area: Malahide, Dublin
Join Date: May 2004
Location: Dublin
Posts: 1,803
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Quote:
Originally posted by Burty
spent ages reading posts on S + F last night it seems they think that the height for optimum speed is between 1" and 1 1/2" above but i'm worried this may be a little high.
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How much setback have you got?
Most people on S&F with your style hull run miles of setback, like 2-3' on some of the progressions. This extra setback puts the prop deeper in the water as the boat runs at an angle not flat, so you have to go higher on the jackplate to compensate.
Well thats my interpretation of it anyway
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08-11-2004, 11:18 PM
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#8
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BananaShark Member
Country: UK
Location: Salcombe South Devon
Occupation: Racer and builder
Interests: Winning races
Boat name: BananaShark
Boat make: BananaShark 34' Race
Engines: Twin Yanmar BY 260's
Join Date: Mar 2004
Location: Salcombe South Devon
Posts: 4,638
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We run about 8" setback plus a Stainless Marine lifter but the height varies from hull to hull - get a GPS and watch both that and the water pressure guage - if the boat starts going sideways or you start loosing water pressure, or it starts gong slower get it down and fast!
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Cookee
British Champions! RIB Formula 1 2005
National Speed Record Holder at 90.15 (still)
www.bananasharkracing.com
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08-11-2004, 11:20 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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got 7 1/2" of setback.
just trying to set it up so if its real flat calm i can go for it but don't want to loose the handleing when rough
i.e if i can go 1" above it will only go 5" below but is that enough????
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09-11-2004, 08:36 AM
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#10
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Registered User
Country: England
Location: South West
Occupation: Development engineer
Interests: Fast boats
Boat name: Xtreme
Boat make: Bernico 21
Engines: Mercury F1, 300 Drag, XR2 "Fingerported"
Cruising area: South West
Join Date: Mar 2004
Location: South West
Posts: 1,043
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Burty why are you asking questions that you already know the answer to.
3" below pad is more than you will ever need for rough conditions
As for optimum height 1-1.5" above pad is going to take some holding on to....be very careful.
Seems like you are changing your spec all the time, you told me that you wanted the engine high for trailering.
Go to short shaft, better handling on a P20
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09-11-2004, 12:54 PM
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#11
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hello
Join Date: Mar 2004
Posts: 2,739
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Quote:
Originally posted by Cyco
3" below pad is more than you will ever need for rough conditions
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Red's about 3" below the pad and its mint in the rough
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09-11-2004, 06:12 PM
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#12
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Senior Member
Country: ingland
Location: rinng faktery
Occupation: lanimayter
Boat name: rinng peas
Join Date: Mar 2004
Location: rinng faktery
Posts: 453
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wy duz dat bote dryver inn de pikk av a orinj catt kennil onn iz fkin hed
gArf
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luk arfter nummber wan. downt stepp inn nummber too
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09-11-2004, 07:20 PM
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#13
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The Doc
Join Date: Mar 2004
Posts: 8,291
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I thought it was a spud croquet placed cunningly in the forground
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11-11-2004, 04:14 PM
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#14
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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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Dude, u know i wana go faster than u.
if it means running 1 1/2" above and hanging on for grim death then i'll do it. spose i'd best pay you for the work before it ends up at the bottom of the sea though a
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11-11-2004, 04:15 PM
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#15
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Registered User
Country: England
Location: South West
Occupation: Development engineer
Interests: Fast boats
Boat name: Xtreme
Boat make: Bernico 21
Engines: Mercury F1, 300 Drag, XR2 "Fingerported"
Cruising area: South West
Join Date: Mar 2004
Location: South West
Posts: 1,043
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Dude you know I'd claim salvage anyway
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12-11-2004, 12:13 AM
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#16
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hello
Join Date: Mar 2004
Posts: 2,739
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No you wouldnt cause I've moved me engine up three holes so I'd get there first
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