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Old 25 April 2017, 19:59   #1
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Country: UK - Channel Islands
Town: Guernsey
Boat name: Eau one
Make: Ribeye
Length: 6m +
Engine: Outboard
Join Date: Sep 2016
Posts: 4
Best prop?

Any help with this would be much appreciated, I have a ribeye 650s which used to have a 150hp Yam fourstroke. Unfortunately it had a head problem, I went down the route of replacing it with a 2013 mariner 2 stroke optimax. The prop that came with the engine at full throttle only allows me to get the rpm up to 5030 and 32 knots! Obvoiusly a two stroke has its power high up the rev range, and with the old four stroke in good conditions I would easily see over 40 knots flat out on the Gps. I was hoping with the 2 stroke even more. What would be peoples suggestions be on past or present rigs. Thanks in advance Ben
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Old 25 April 2017, 21:23   #2
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Country: UK - Scotland
Length: 4m +
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Quote:
Originally Posted by Benj1983 View Post
Any help with this would be much appreciated, I have a ribeye 650s which used to have a 150hp Yam fourstroke. Unfortunately it had a head problem, I went down the route of replacing it with a 2013 mariner 2 stroke optimax. The prop that came with the engine at full throttle only allows me to get the rpm up to 5030 and 32 knots! Obvoiusly a two stroke has its power high up the rev range, and with the old four stroke in good conditions I would easily see over 40 knots flat out on the Gps. I was hoping with the 2 stroke even more. What would be peoples suggestions be on past or present rigs. Thanks in advance Ben

Usually a prop with a higher pitch, will give a better top speed. With revs that low perhaps the prop is too large (diameter) a smaller prop will allow the engine to rev higher it's all about playing with it and testing untill u get it perfect for the boat and engine.
Regards
Andrew
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Old 26 April 2017, 08:55   #3
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Country: UK - England
Town: Leicester
Length: 5m +
Engine: 135hp Mercury
Join Date: Sep 2013
Posts: 1,408
Usual advice:
Look up the engine manufacturer's Wide Open Throttle (WOT) range for that engine.
Take your boat out with its normal load & make several runs at WOT & note the achieved RPM.
Once you have that figure you can then look at props that will give you nearer to what you are looking for whilst staying within the WOT range.
Mercury - and others - have apps you can enter your details into that will give their suggestions: https://www.mercurymarine.com/en/us/...tor/#/step-one
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Old 26 April 2017, 09:57   #4
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Country: UK - England
Town: Retford
Boat name: Spy-sea-one
Make: Excel 435
Length: 4m +
Engine: Suzuki Outboard/25/4
Join Date: Oct 2011
Posts: 7,441
RIBase
https://www.propeller-shop.eu/propeller-info/

might help
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Old 26 April 2017, 14:48   #5
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Country: UK - England
Town: Chesterfield
Boat name: Sea Quell
Make: Picton Cobra
Length: 5m +
Engine: Mercury 150 4 Stroke
MMSI: 235038298
Join Date: Sep 2003
Posts: 1,095
Quote:
Originally Posted by Benj1983 View Post
Any help with this would be much appreciated, I have a ribeye 650s which used to have a 150hp Yam fourstroke. Unfortunately it had a head problem, I went down the route of replacing it with a 2013 mariner 2 stroke optimax. The prop that came with the engine at full throttle only allows me to get the rpm up to 5030 and 32 knots! Obvoiusly a two stroke has its power high up the rev range, and with the old four stroke in good conditions I would easily see over 40 knots flat out on the Gps. I was hoping with the 2 stroke even more. What would be peoples suggestions be on past or present rigs. Thanks in advance Ben
What pitch is your current prop ? Based on your current revs, you would most likely need at least 2" less pitch to get into the 5600-5750 range - assuming the same model of prop. Its probably a laser II ??
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