Just bought a rib!! - Help please

MOON · 23 June 2008, 21:28

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

reinier · 23 June 2008, 22:23

Expect just under 35 knots with this setup.

Nos4r2 · 23 June 2008, 23:20

Quote:

Originally Posted by MOON

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.

MOON · 24 June 2008, 06:44

Quote:

Originally Posted by MOON

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

reinier · 24 June 2008, 07:03

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.

MOON · 24 June 2008, 07:21

Thanks reiner

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

cheers

Colin

Pete7 · 24 June 2008, 08:04

Quote:

Originally Posted by MOON

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

reinier · 24 June 2008, 12:40

Quote:

Originally Posted by MOON

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.