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05 June 2012, 15:59
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#1
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Member
Join Date: Jun 2012
Posts: 3
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Yamaha 115 four stroke
I have a 2005 115 Yamaha on a 6.2 meter rib. I get about 38 mph top end on a 13 x 19" prop and revs about 5800, I would like a little more, any help
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05 June 2012, 16:37
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#2
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Member
Country: USA
Town: Seattle
Boat name: Water Dog
Make: Polaris
Length: 4m +
Engine: Yamaha 60hp
Join Date: Apr 2007
Posts: 1,152
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Quote:
Originally Posted by 6.2Avon
I have a 2005 115 Yamaha on a 6.2 meter rib. I get about 38 mph top end on a 13 x 19" prop and revs about 5800, I would like a little more, any help
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There's no more there. Try taking unused gear out of the boat so its lighter.
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05 June 2012, 16:48
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#3
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Member
Country: USA
Town: Oakland CA
Length: 3m +
Join Date: Feb 2005
Posts: 6,653
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You've got a couple more thousand rpm before max WOT, so you *may* be able to squeeze a couple more mph out of it. Jack's got the best first step.
But:
F115 can take up to a 14" diameter prop; you might try finding a prop to meet the following:
1) Drop the pitch by a couple of inches and up the diameter by about 3/4"
2) Either find or rework the prop to an 18" pitch (same diameter.)
3) Rework existing prop to reduce cupping a bit (If SS; Aluminum typically doesn't have any cupping)
All trial and error, but it's the only way you're going to get more out of a near-correct setup.
jky
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05 June 2012, 17:00
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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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Quote:
Originally Posted by jyasaki
You've got a couple more thousand rpm before max WOT, so you *may* be able to squeeze a couple more mph out of it. Jack's got the best first step.
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Your joking aren't you, do you mean a couple of hundred more?!
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05 June 2012, 17:04
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#5
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Member
Join Date: Jun 2010
Posts: 2,934
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buy a bigger engine if you want more power really. your at your max there just about with 5800rpm. you'll spend a lot of money and get no more than 2/3mph.
cheers
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05 June 2012, 20:10
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#6
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Member
Join Date: Jun 2012
Posts: 3
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Cheers, I thought as much. Etec it is then. Save save save
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05 June 2012, 20:49
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#7
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Member
Country: USA
Town: Oakland CA
Length: 3m +
Join Date: Feb 2005
Posts: 6,653
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Quote:
Originally Posted by chewy
Your joking aren't you, do you mean a couple of hundred more?!
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Woops.
Hundred is right.
jky
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11 June 2012, 18:55
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#8
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Member
Country: UK - England
Town: plymouth
Boat name: teal
Make: crompton
Length: 7m +
Engine: 2 x 100 yamaha
Join Date: Mar 2008
Posts: 31
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agree with all said, but will add, worth looking at the engine and ensure it is running its most efficient.
shaun
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12 June 2012, 11:40
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#9
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Member
Country: USA
Town: Northport
Boat name: Zazu
Make: Nautica
Length: 7m +
Engine: outboard
Join Date: Apr 2012
Posts: 37
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We had a similar setup with the same engine and had a few more mph most of the time with a 19" prop dependent upon loading.
- Check the height of the anti vent plate at speed and see if you are too low.
- Are you or can you trim up sufficiently?
- How heavily are you loaded for and aft when looking for speed?
Hope this helps
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12 June 2012, 20:46
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#10
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Member
Country: UK - England
Town: Fareham
Length: 6m +
Join Date: Sep 2003
Posts: 7,866
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Stop chasing that golden nugget and concentrate on getting the highest cruising speed with the best fuel economy 
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Andy
Looks Slow but is Fast
Member of the ebay Blue RIB cover club.
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