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Old 18 October 2009, 16:17   #1
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Country: UK - England
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Boat name: Rocky
Make: Ribcraft
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Ribcraft 4.8 Yam 90 2stroke prop

Hi
I was wondering if anyone might be able to help me.

I recently bought a stunning ribcraft 4.8, it came with an etec 75 (which I had to sell sadly)

I have put my 2000ish yam 90 2 stroke outboard on it.

I was wondering if anyone had a good idea of what prop should be on it, at the moment I have a very chewed up ally one and looking to replace with a stainless one as a christmas present to myself.

Many thanks

Tim
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Old 18 October 2009, 16:33   #2
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Yam 90 on a Ribcraft 4.8?
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Old 18 October 2009, 16:34   #3
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Quote:
Originally Posted by rockyrib View Post
Hi
I was wondering if anyone might be able to help me.

I recently bought a stunning ribcraft 4.8, it came with an etec 75 (which I had to sell sadly)

I have put my 2000ish yam 90 2 stroke outboard on it.

I was wondering if anyone had a good idea of what prop should be on it, at the moment I have a very chewed up ally one and looking to replace with a stainless one as a christmas present to myself.

Many thanks

Tim
Chrikey a 90 on a 4.8?????
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Old 18 October 2009, 16:35   #4
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Originally Posted by Downhilldai View Post
Yam 90 on a Ribcraft 4.8?
You beat me to it.
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Old 18 October 2009, 16:41   #5
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Country: UK - England
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Hmm
Yep its rather tasty, I got 42mph on the gps with a wrecked prop (its a trade up from my avon 3.45 with a yam 40)
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Old 18 October 2009, 17:03   #6
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, blimey, well, over the power rating ..anyway as the engine weighs only 120 kg which is well under the Max weight , try a 13 x 19 ally lets see some pics of her
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Old 19 October 2009, 04:15   #7
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rockyrib if I were you I put put a higher pitch prop on that set up . you dont want too over rev that outboard man and blow the powerhead up . I have seen a 5metre with the same engine and the guy was running a 17 and was reving @ 5800 on W.O.T and the poor powerhead lasted 6 hours . he the customer was so happy as he was getting those revs but didnt really know what he was about to come across . YES a piston thru the block . So my advice and experience would be higher pitch too drop the revs . baz
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Old 20 October 2009, 11:34   #8
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My Novamarine 4.5 metre runs a Yamaha 60 2 stroke. I was reaching a screaming 5900 at WOT on a 15 inch prop so quickly upgraded prop to a 21 inch and its perfect now, topping out at 4950 at 5mph faster. This is a very light boat though. 190kgs ex engine! People with larger ribs think I am very odd running a 21 inch prop with only 60 hp, but its a great setup.

The place I got my prop from on ebay had another Yamaha 23 incher. In fact they have been relisting it for months. The number of customers who need to run a prop of such big pitch on an engine so small (15 spline 4.25 inch gearcase) is probably limited. The item is at http://cgi.ebay.co.uk/propellor-prop...item2ea68336df

I'm not garanteeing it will be right but its easier to work down pitches than up as there's less risk of blowing the powerhead up.
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Old 20 October 2009, 18:23   #9
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Hi Guys,
Thanks for all the help, I have decided to buy an ally prop first just to give it a go and see wether the one I buy is right before going for the stainless baby.

I have bought the one on ebay - 60 seemed dead cheap and I had a few quid in my paypal balance.

This may sound really stupid but can anyone just point out what the numbers mean I guess the pitch is the angle of the blades and the other measurement is the diameter?

So the one I got : 12 5/8 x 23
I guess the 12 5/8's is the pitch and the 23 the size of the blades?

Sorry for sound stupid

Tim
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Old 20 October 2009, 18:31   #10
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Quote:
Originally Posted by rockyrib View Post
Hi Guys,
Thanks for all the help, I have decided to buy an ally prop first just to give it a go and see wether the one I buy is right before going for the stainless baby.

I have bought the one on ebay - 60 seemed dead cheap and I had a few quid in my paypal balance.

This may sound really stupid but can anyone just point out what the numbers mean I guess the pitch is the angle of the blades and the other measurement is the diameter?

So the one I got : 12 5/8 x 23
I guess the 12 5/8's is the pitch and the 23 the size of the blades?

Sorry for sound stupid

Tim

12 5/8" will be the diameter and 23" the pitch, ie how much one revolution of the prop will move you forward in the water without any slip.
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