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Old 23 June 2008, 17:28   #1
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Country: UK - England
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Just bought a rib!! - Help please

Few questions hope you can help!
Just bought a 1996 opsrey viper 5.25 fitted with twin 60hp 3 cylinder '96 engines

Will champion L-3G plugs be suitable for the engines? ( I was given six and told they would but not seen them listed anywhere.) If so what should the gap size be?
What is the optimum RPM for these engines?
Both fitted with 4873140A4015P props roughly what top speed should I be getting in knots with this set up. (with good props)
Has anybody got one of these props for sale as one is damaged?

Thanks for your help guys
Matt (helicopterman) thanks for your advice

Colin and elizabeth
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Old 23 June 2008, 18:23   #2
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Expect just under 35 knots with this setup.
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Old 23 June 2008, 19:20   #3
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Quote:
Originally Posted by MOON View Post
Few questions hope you can help!
Just bought a 1996 opsrey viper 5.25 fitted with twin 60hp 3 cylinder '96 engines

Will champion L-3G plugs be suitable for the engines? ( I was given six and told they would but not seen them listed anywhere.) If so what should the gap size be?
What is the optimum RPM for these engines?
Both fitted with 4873140A4015P props roughly what top speed should I be getting in knots with this set up. (with good props)
Has anybody got one of these props for sale as one is damaged?

Thanks for your help guys
Matt (helicopterman) thanks for your advice

Colin and elizabeth
Welcome to RibNet
L3G is equivalent to NGK B8HV

Manual for '96 60hp specs NGK BP8H-N-10 (check these are set to 1mm gap)which don't appear to have a direct Champion equivalent.

I suspect the L3G WILL work if it's the same thread length as the NGK BP8H-N-10 as they are the same heat rating-but you probably won't get the performance you would from the NGKs.
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Old 24 June 2008, 02:44   #4
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New rib help

Quote:
Originally Posted by MOON View Post
Few questions hope you can help!
Just bought a 1996 opsrey viper 5.25 fitted with twin 60hp 3 cylinder '96 engines

Will champion L-3G plugs be suitable for the engines? ( I was given six and told they would but not seen them listed anywhere.) If so what should the gap size be?
What is the optimum RPM for these engines?
Both fitted with 4873140A4015P props roughly what top speed should I be getting in knots with this set up. (with good props)
Has anybody got one of these props for sale as one is damaged?

Thanks for your help guys
Matt (helicopterman) thanks for your advice

Colin and elizabeth
Thanks for the replies guys

Can anybody help with the remaining questions?
What is the optimum RPM for these engines?
Both fitted with 4873140A4015P props roughly what top speed should I be getting in knots with this set up. (with good props)
Has anybody got one of these props for sale as one is damaged? Or can you recommend someone who can repair for a sensible price?

Thanks again

Colin and Elizabeth
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Old 24 June 2008, 03:03   #5
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Max RPM range for your engines is 5000 - 6000 rpm. Peak HP @ 5500rpm.

So 5500rpm is what you want to reach. With those props you'll get a speed just under 35 knots, like 33,5 or 34.
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Old 24 June 2008, 03:21   #6
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New rib help

Thanks reiner

What would I need to do to get 35knots out of her?

cheers

Colin
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Old 24 June 2008, 04:04   #7
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Thanks reiner, What would I need to do to get 35knots out of her? cheers Colin
Colin, thats probably your lot. To go faster you need either more hp or less weight. Assuming changing the engines is not an option at the moment, your other options is to empty the boat of anything you don't need, remove the A frame and windscreen, put your passengers on a diet and carry the minimum amount of fuel.

Personally I wouldn't bother. 35 knots in 5.25 rib is quite fast enough and in most sea conditions you won't be able to run at that speed so even greater performance becomes irrevelant.

Great rib btw and very well thought of on here she will cross the channel in good weather if you want, but do fix that prop sooner rather than later. Then check that you can achieve max revs on flat calm water with normal load, this will confirm you have the right size props and give the best performance and fuel economy.

Pete
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Old 24 June 2008, 08:40   #8
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Thanks reiner

What would I need to do to get 35knots out of her?

cheers

Colin
Maybe you can test some stainless steel props, and lift the engines an inch or two with those props. But that is a really expensive change because you need 2 props instead of one. 700 pounds for maybe a 1 or 2 knot increase in speed isn't worth it I think.
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Old 24 June 2008, 12:56   #9
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Thanks reiner

What would I need to do to get 35knots out of her?

cheers

Colin
Flog the twin 60s and fit a single 90 or 100
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Old 24 June 2008, 15:53   #10
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spark plug gaps

Hi
Bought the plugs today how do I go about changing the gap to 1mm? Is there a tool to do it?
Thanks for all you advice

Colin and Eli
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