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Old 05 June 2012, 11:59   #1
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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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Old 05 June 2012, 12:37   #2
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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
There's no more there. Try taking unused gear out of the boat so its lighter.
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Old 05 June 2012, 12:48   #3
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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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Old 05 June 2012, 13:00   #4
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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.
Your joking aren't you, do you mean a couple of hundred more?!
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Old 05 June 2012, 13:04   #5
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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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Old 05 June 2012, 16:10   #6
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Cheers, I thought as much. Etec it is then. Save save save
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Old 05 June 2012, 16:49   #7
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Your joking aren't you, do you mean a couple of hundred more?!
Woops.

Hundred is right.

jky
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Old 11 June 2012, 14:55   #8
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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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Old 12 June 2012, 07:40   #9
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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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Old 12 June 2012, 16:46   #10
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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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