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Old 03 November 2003, 12:18   #1
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Country: UK - England
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props

Hi to all on Ribnet

Firstly may I say what a great site this is. I was wondering if anyone could give me some advise as i've not been ribbing for that long. I have a Delta 6.5m high bow with twin suzuki 65s the props are standard and have a 15 degree pitch I want to go for stainless ones but keep reading about different pitch etc. Could someone please advise me on what to go for as I have no idea.
Thanks Shaun.
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Old 03 November 2003, 12:46   #2
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Hi Shaun,

Welcome to RIB net!

You need to know what rpm the engines are achieving at WOT (wide open throttle) and what the manufacturer's recommended (and maximum) rpm ranges are for your engine(s). Then you'll know if your engines are currently operating efficiently.

Then you can start to work out if you need a different size prop.

I did this recently for mine and gained another 4kts.... until the new prop fell apart!

Are you using aluminium props at the moment?

I guess that most of the prop calculator programs don't cater for twin engine installations?

BTW did you buy your RIB from Nationwide Boat Sales?

Richard.
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Old 03 November 2003, 13:15   #3
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Hi Richard
Thanks for replying, yes the props are alimimium,and yes I did buy it from Nationwide boat sales. Do you know anything about it?
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Old 03 November 2003, 13:33   #4
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No - no probs... just that I nearly drove up the M1 to look at that RIB as it looked like an excellent bargain. But by the time I'd got my cash together, it was sold to someone!
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Old 05 November 2003, 15:23   #5
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Re: props

Quote:
Originally posted by Shaun
Hi to all on Ribnet

.... the props are standard and have a 15 degree pitch I want to go for stainless ones but keep reading about different pitch etc.
I think you mean 15 INCH pitch.... That's the theoretical distance your prop would travel through a solid during one revolution.

I had 15" props on my Ribcraft 5.85 with twin 65hp mariners. They were fine and the engines got up to the manufacturers recomended WOT RPM..... just!

Since yours is a bigger and presumably heavier boat.... and since you're talking about s/s props which, I am told, grip the water better, you may find it worth trying out a pair of 13" props just to see how it goes...... but at about 250 each, I'd borrow them first. You should get aluminium ones for around 100 each!

As Richard B said, it really is suck it and see.... what your WOT brings! I certainly wouldn't think any more than 15" though!

Mike C
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Old 05 November 2003, 15:33   #6
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Keep trying different props untill you get the right one for your boat. You could try 4 bladed props too...theoretically less efficent on a high reving engine but always worth a try.

Also dont chose your prop WOT on flat water trimmed right out because you will never reach that RPM out at sea. I had me boat on windermere last week and i have never ever seen the rev counter go that high in 3 years of ribing on the sea.
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Old 05 November 2003, 15:44   #7
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Not quite the same in a deep-V larger RIB. 'specially in a Delta which should punch it's way thru' the chop very nicely indeed.

Be as scientific as possible - saves on purchasing lots of useless props. Let us know how you get on Shaun, if only to tell us what rpm and speed you're getting at WOT at the moment.
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Old 05 November 2003, 16:28   #8
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Richard B,

I'm suprised to see you handing out advice on subject that you clearly have no knowledge of !!!
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Old 05 November 2003, 16:50   #9
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oops, wrong login!
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Old 05 November 2003, 16:52   #10
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Be a little more introspective, Dirk. You're the one who advised his customer to buy a "get you home" prop which clearly won't do what it says on the tin. Have you recalled that faulty component from your customer? Or would that mean that you'd have to admit that you've got it wrong? Heaven forbid!
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