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14-10-2004, 04:47 PM
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#21
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Registered User
Country: Essex
Location: Great Stambridge Essex
Occupation: Director Paving company
Interests: Boating/Squash
Cruising area: Essex Marina/crouch southeast coast
Join Date: Sep 2004
Location: Great Stambridge Essex
Posts: 2,033
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pretty sure im just going to try moving the trim tabs down abit and move the fuel tank to the front all i can think is it was ok with the xr2 on there now ive got another 200lb on the back it must be the weight
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14-10-2004, 04:48 PM
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#22
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The Doc
Join Date: Mar 2004
Posts: 8,291
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Quote:
Originally posted by Matt
Yeh captain, but your Y-fronts have skids in before you even start cos you never wash them.
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i'm Sprung!
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14-10-2004, 06:02 PM
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#23
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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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Dunno what lower unit they have, but if it's a less 'speed friendly' profile, you could be experiencing 'blow out', however, I would have thought 70 was a little slow to be getting this.
Also, (I'm assuming the lower unit ratio is 1.87:1), 5000rpm on a 25" prop only figures to about 57 mph.
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"I Agree with everything you say really!" - John Cooke to Jon Fuller - 26-01-2013
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14-10-2004, 06:35 PM
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#24
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The Doc
Join Date: Mar 2004
Posts: 8,291
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So that merc came off a searay then!
Sorry....thats the most constructive comment all day!
Anyway........dont go knockin the Taz you guys!! he got his motor over pretty goddam cheap!
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14-10-2004, 06:54 PM
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#25
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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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I'm not knocking anyone, just trying to be constructive, but sometimes working out the numbers can put things in perspective, not all speedos/GPS's are accurate, that's all.
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"I Agree with everything you say really!" - John Cooke to Jon Fuller - 26-01-2013
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14-10-2004, 07:12 PM
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#26
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Registered User
Country: Essex
Location: Great Stambridge Essex
Occupation: Director Paving company
Interests: Boating/Squash
Cruising area: Essex Marina/crouch southeast coast
Join Date: Sep 2004
Location: Great Stambridge Essex
Posts: 2,033
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Whats blow out johnson?. Well if my gps is wrong i know its faster then my old xr2 cos a friend has got a ring with an xr2, hes boat was faster then mine fitted with my xr2 now my boat fitted with 275 is like warp factor nine compared!
Good luck understanding that sentence.
And i know its not very accurate but the speedo on the boat sits at 70mph.
I did hear that mph on water was different from land is this true or boxxocks?
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14-10-2004, 07:22 PM
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#27
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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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MPH are MPH.
'Blow out' is when the profile (for want of a better description, how pointed and fine an entry it is) is a little too blunt, and the bullet, or gear case fwd of the prop is too short, and basically, when you get beyond a certain speed, the blunt entry spreads the water so quickly and abruptly, that the water flow is unable to follow the contours of the casing, and digs a bigger hole in the water than the diameter of the gear case itself, this then allows the propeller to ventilate, or cavitate, the revs climb and the speed falls until you are again below blowout speed.
Clear as mud? I'm not too good at explanations, will try to find a drawing, or do a sketch myself.
JF
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"I Agree with everything you say really!" - John Cooke to Jon Fuller - 26-01-2013
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14-10-2004, 08:05 PM
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#28
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Registered User
Country: Essex
Location: Great Stambridge Essex
Occupation: Director Paving company
Interests: Boating/Squash
Cruising area: Essex Marina/crouch southeast coast
Join Date: Sep 2004
Location: Great Stambridge Essex
Posts: 2,033
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So will lifting the engine stop it digging in the water? or plastic fins bolted to the lower unit? i know i bolted a pair to an old 80 merc to help in planning.
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14-10-2004, 08:07 PM
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#29
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Registered User
Country: Essex
Location: Great Stambridge Essex
Occupation: Director Paving company
Interests: Boating/Squash
Cruising area: Essex Marina/crouch southeast coast
Join Date: Sep 2004
Location: Great Stambridge Essex
Posts: 2,033
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Although holding the throttle at the same amount does not appear to slow the boat down and nor does the revs raise with out touching the throttle
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14-10-2004, 08:40 PM
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#30
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Registered User
Country: Essex
Location: Great Stambridge Essex
Occupation: Director Paving company
Interests: Boating/Squash
Cruising area: Essex Marina/crouch southeast coast
Join Date: Sep 2004
Location: Great Stambridge Essex
Posts: 2,033
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Engine mounted centre bolted straight into old xr2 holes def 25 picth prop like new. at the rear of boat is lots of steel for ski pole and reinforcing transom fuel tank big battery oil resevoir power trim pump. manual trim tabs. bow tank fitted to front
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14-10-2004, 08:41 PM
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#31
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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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Quote:
Originally posted by Johnson
Dunno what lower unit they have, but if it's a less 'speed friendly' profile, you could be experiencing 'blow out', however, I would have thought 70 was a little slow to be getting this.
Also, (I'm assuming the lower unit ratio is 1.87:1), 5000rpm on a 25" prop only figures to about 57 mph.
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And that's being charitable assuming only 10% slip.
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14-10-2004, 10:10 PM
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#32
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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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Quote:
Originally posted by Ned
And that's being charitable assuming only 10% slip.
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Yeah, my twin just about manages 10/11% with relatively low 'X'
Hey Taz, you say it has 'manual trim tabs', where are they set, ie, if you were to put a straight edge along the hull in line with the tabs, would the tail of the tab stop the straight edge touching the boat at the transom?
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14-10-2004, 11:28 PM
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#33
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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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Quote:
Originally posted by Johnson
Yeah, my twin just about manages 10/11% with relatively low 'X'
Hey Taz, you say it has 'manual trim tabs', where are they set, ie, if you were to put a straight edge along the hull in line with the tabs, would the tail of the tab stop the straight edge touching the boat at the transom?
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There are more than one of you?
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14-10-2004, 11:31 PM
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#34
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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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14-10-2004, 11:33 PM
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#35
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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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Quote:
Originally posted by Matt
I think the box ratio is 1.6, maybe 1.62. This makes the sums add up a lot better.
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Ah, now that'd change things, surprised at that ratio tho' with them being more an 'open fisher' type motor, rather than a super sports.
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14-10-2004, 11:34 PM
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#36
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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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Well I don't like to brag
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"I Agree with everything you say really!" - John Cooke to Jon Fuller - 26-01-2013
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14-10-2004, 11:38 PM
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#37
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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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they really aren't the quickest thing around tho' TD did some work on Ring 21 (cuddy cabin, like his 21) with a 275 on a bracket, I don't think it did much over 60, imagine that boat with a 2.4 efi (245hp) or a 2.5 efi (265hp) it'd be lively.
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"I Agree with everything you say really!" - John Cooke to Jon Fuller - 26-01-2013
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15-10-2004, 12:09 AM
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#38
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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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No, we just tend to be a bit more reserved than our cousins on the other side of the pond. By the way, the correct spelling is humor. As in harbor, color, demeanor et. al.
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15-10-2004, 12:15 AM
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#39
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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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Quote:
Originally posted by Ned
No, we just tend to be a bit more reserved than our cousins on the other side of the pond. By the way, the correct spelling is humor. As in harbor, color, demeanor et. al.
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15-10-2004, 12:19 AM
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#40
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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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Quite
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