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01 April 2010, 08:03
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#1
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Member
Country: UK - Scotland
Boat name: Wildheart
Make: Humber/Delta Seasafe
Length: 5m +
Engine: Merc 60 Clamshell
MMSI: 235068449
Join Date: Apr 2007
Posts: 4,670
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Twin engines not performing
Quick one for you guys with twins.
While I am rebuilding the merc I thought I try a twin Johnson setup, but I'm just not getting the performanceI was expecting.
I have two Johnsons, perfectly matched, props identical, both tuned to run at the same Vmax. I just cant seem to get the top speed I was expecting. I'll post pics later for analysis.
Help?
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01 April 2010, 09:30
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#2
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Member
Country: UK - England
Town: Up Norf
Make: Avon SR4,Tremlett 23
Length: 4m +
Engine: Yam 55, Volvo 200
Join Date: Apr 2007
Posts: 5,217
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What size engines on what boat?
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01 April 2010, 09:35
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#3
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Member
Country: UK - Scotland
Boat name: Wildheart
Make: Humber/Delta Seasafe
Length: 5m +
Engine: Merc 60 Clamshell
MMSI: 235068449
Join Date: Apr 2007
Posts: 4,670
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A couple of Johnson Single cylinders, Mid 70s vintage. old engines, but the were to hand.
Temporarily dropped on the humber while the merc gets rebuilt
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01 April 2010, 09:39
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#4
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Member
Country: UK - England
Town: Up Norf
Make: Avon SR4,Tremlett 23
Length: 4m +
Engine: Yam 55, Volvo 200
Join Date: Apr 2007
Posts: 5,217
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Single cylinder, can't be much hp? How longs the Humber?
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01 April 2010, 09:49
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#5
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Member
Country: UK - Scotland
Boat name: Wildheart
Make: Humber/Delta Seasafe
Length: 5m +
Engine: Merc 60 Clamshell
MMSI: 235068449
Join Date: Apr 2007
Posts: 4,670
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remember there were 2-pot 70 and 80 Hps kicking about back then.........
5m.
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01 April 2010, 09:50
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#6
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Member
Country: UK - England
Town: Up Norf
Make: Avon SR4,Tremlett 23
Length: 4m +
Engine: Yam 55, Volvo 200
Join Date: Apr 2007
Posts: 5,217
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So do you know what hp they are?
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01 April 2010, 09:58
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#7
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Member
Country: UK - Scotland
Boat name: Wildheart
Make: Humber/Delta Seasafe
Length: 5m +
Engine: Merc 60 Clamshell
MMSI: 235068449
Join Date: Apr 2007
Posts: 4,670
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Here's a pic of the setup:
(sorry, couldn't keep this going 'till 12..........)  
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01 April 2010, 10:04
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#8
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Member
Country: UK - England
Town: PORTSMOUTH
Make: Avon 5.4, Avon 3.4,
Length: 5m +
Engine: Yamaha 90, Merc 30
Join Date: Sep 2003
Posts: 1,976
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01 April 2010, 10:20
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#9
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Member
Country: UK - Scotland
Boat name: Wildheart
Make: Humber/Delta Seasafe
Length: 5m +
Engine: Merc 60 Clamshell
MMSI: 235068449
Join Date: Apr 2007
Posts: 4,670
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 Happy new April! 
To be honest without the main engine on there I'm not sure the props would even touch the water!
Just for the record, I took that as a joke just before I started stripping the transom down and been waiting for 3 months for a suitable day to use it! 
This is what was under three layers of "rescue orange", and will be the subject of a "refurb" thread in a few weeks when it's all back together.
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01 April 2010, 15:09
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#10
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Member
Country: UK - England
Town: Up Norf
Make: Avon SR4,Tremlett 23
Length: 4m +
Engine: Yam 55, Volvo 200
Join Date: Apr 2007
Posts: 5,217
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I know where there is a 3rd one if you need it!
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01 April 2010, 15:43
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#11
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Member
Country: UK - England
Town: yorkshire
Boat name: little vicky
Make: avon ex RNLI
Length: 3m +
Engine: tohatsu
Join Date: Mar 2008
Posts: 2,310
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,,you could try doel fins ,,most people seem to say they improve performance ,,though there wont be much to bolt too ,,or,,,you could try moving some weight forward that might improve things though i dont think your going to get your eyes streeming with the wind rushing past ,,LOL good one !
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02 April 2010, 08:04
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#12
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Member
Country: UK - Scotland
Boat name: Wildheart
Make: Humber/Delta Seasafe
Length: 5m +
Engine: Merc 60 Clamshell
MMSI: 235068449
Join Date: Apr 2007
Posts: 4,670
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Quote:
Originally Posted by chewy
I know where there is a 3rd one if you need it!
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I could move them to the edges of the cut-out & get my Aux in the middle - double the available Hp!
Quote:
Originally Posted by m chappelow
,,you could try doel fins ,,most people seem to say they improve performance ,,though there wont be much to bolt too ,,or,,,you could try moving some weight forward that might improve things though i dont think your going to get your eyes streeming with the wind rushing past ,,LOL good one !
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I think the only way that's going to get my eyes streaming is by crying through boredom!
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