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Old 25 January 2013, 07:12   #1
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Right Prop for a Yamaha 90 on 6m Ribeye?

Hi - I'm new to this forum but hope someone can help me with some advise on the best pitch prop for my 2004 6m Ribeye. It has a 90 Yamaha 2-stroke engine and currently a 17 degree pitch alloy prop. However, I'm disappionted with the top speed - about 30 knots - and also the rev limit - I can't get any more thsn 4500. It gets up onto the plane fine - but I'd like more top speed. I've been advise to go for a 15 degree pitch. Anyone had this sort of experience? Regards Richard in Christchurch.
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Old 25 January 2013, 07:35   #2
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If you're not getting 5500rpm your not getting 90hp. A 5.4 searider with 85yam will do 5500rpm with 17.5x15K prop. If you mount engine up one hole with cav plate an inch above base, lighter steering and an additional 100 rpm, they will cope with this but really 5500 is max recommended.
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Old 25 January 2013, 07:40   #3
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Sorry 13.5x15k

You get additional 300hp per inch of pitch lower. Is your 90hp ok as I would expect more from a 17?
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Old 25 January 2013, 07:56   #4
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Check that the tachometer is set correctly. Speed at 30kn seems ok ish for the prop but the rpm sounds wrong. Is tachometer set to 12 pole. I could be wrong about that as I'm going back years, but I think it is. What tachometer is it?
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Old 25 January 2013, 08:46   #5
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FWIW I have an 85hp 2 stroke with a 13.5x15 prop on a Humber Attaque 5.35. It sails through 5500 if I'm not careful with the throttle. Been thinking I ought to move up to 16 (if available) or 17 when funds allow. Admittedly the Attaque is supposed to be quite a 'slight' 5m and it was only carrying 3 peeps and 50l of fuel at the time. Dunno what this means, if anything, for the OP.
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Old 25 January 2013, 09:36   #6
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Sorry again 300 RPM per inch of pitch. Searider I used also had A Frame & Self Righting Bag
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Old 26 January 2013, 10:57   #7
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Hi all, thanks for your repies. It looks like I may have to go down to a 15 pitch. However, what difference does the size (diameter) make?
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Old 26 January 2013, 13:55   #8
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Can't answer the question, but depending on the diameter I might be interested in your 17 pitch prop if your thinking on selling.
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Old 26 January 2013, 14:10   #9
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Quote:
Originally Posted by richrib View Post
Hi - I'm new to this forum but hope someone can help me with some advise on the best pitch prop for my 2004 6m Ribeye. It has a 90 Yamaha 2-stroke engine and currently a 17 degree pitch alloy prop. However, I'm disappionted with the top speed - about 30 knots - and also the rev limit - I can't get any more thsn 4500. It gets up onto the plane fine - but I'd like more top speed. I've been advise to go for a 15 degree pitch. Anyone had this sort of experience? Regards Richard in Christchurch.
Richard

I have dug this old 2008 info out

Ten personnel from
Yamaha Europe and UK
spent 3 days at
Dartmouth HQ testing
propeller combinations.
The objective was to
maximise performance
of the Ribeyes i.e.
s p e e d a n d f u e l
efficiency, by matching
the best prop to engine.
The preferred prop for
the 785 powered by a
Yamaha F250 was the
Pro Series 23.
The 650 with F150 combination
tested best with
the Black Stainless Steel
19.
The best choice and best
performing propeller for
a Ribeye 600 with
F115was the Performance
Series 18.
Finally the preferred prop
for the 500 with F80 was
the Aluminium 17.
This sort of testing is
vital and all to often not
done by many of the
smaller RIB producers.
If you really want to get
the best out of your boating
it pays to choose a
company that is prepared
to do the research
in this sort of area. The
results are then passed
onto the customer in the
way of high performance
craft operating at their
maximum potential

I would suggest a call to Dartmouth office of Ribeye and ask for the data on prop test, I think they have done a few with Yamaha.
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Old 28 January 2013, 07:51   #10
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Many thanks - called Ribeye and they were v. helpful. I should be getting 34/35 knots at 5000-5500 revs so decided that a 13.5 x 15" pitch was the best fit. Should get me into the low 5000 revs and a better top speed.
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