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Old 14 March 2010, 22:53   #1
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Country: Ireland
Make: ribcraft 7.85
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250 yam prop advice

hi there, just looking for any one out there with ribcraft 7.8 or rib around same size with 250 yamaha 4 stroke. if so what prop do you have on and what you gettin out of it at what rpm? i'd be lookin for something for cruising with light loads, maybe 3 or 4people, at around 25, 30knots ,??any advice would be good
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Old 16 March 2010, 15:47   #2
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it was so busy at ribcraft at the weekend i couldn't even get a good pic of my new [new to me] toy leaving, anyway checked the prop and i,ve 13 3/4 + 19 ,full of fuel ,5 on board, i rev out 6000+ at 44mph, was going to put on a 21 , any one have one on? maybe 23?
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Old 16 March 2010, 18:27   #3
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Country: UK - Scotland
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Make: Scorpion 8.1 mk2
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Engine: Yam F250 4.2 Litre
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Hi Ribdraft,

Your new boat looks great!

That propeller diameter sounds too small to me, in fact, at 13 3/4 it sounds like perhaps a prop of a yamaha F150, with the smaller diameter. It should probably be a Yamaha Saltwater Series II propeller on the F250, which would actually be 15 1/4 X 19.

I dont have a direct comparison, but my friends boat, A Delta 7.4x (heavy built boat)with a Yamaha F225 has a Yamaha Salwater Series II prop fitted, 15 1/4 diameter X 19" pitch and easily hits 52mph (45knots+)

Hope this helps.

Robbie
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Old 16 March 2010, 18:52   #4
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Hi we have a 250 F/stroke on a 8.1 Scorpion
i have tried many props 19 21 and a 23
the 19 over reved and the 23 underreved the 21 was the S/S black it was all right but a bit of cavatation, so i have had the 23 yamaha pro plus re pitched to 21,5 went out on the 7 March and its great, the prop thing is a dark art what suits one seams terrable on another and weight makes a big differance
we have a 400 lt fuel tank and 2 up with a full tank max rpm 5900
44 knts it should rev a bit more.
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Old 16 March 2010, 23:10   #5
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thanks robbie and roy, yeah its a fine dark art alright, i was lucky with last rib as friend had near same rib and engine, he had 4 different sizes so i got to test them all til i found the one i liked [cheers ted] roy sounds like you have it sorted , who did the work for you? 44 knots at 5900, you must be doing 30knots around the 4000rpm??? thats my aim really
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Old 17 March 2010, 11:13   #6
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Make: Ribeye S850 charter
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Quote:
Originally Posted by ribdraft View Post
hi there, just looking for any one out there with ribcraft 7.8 or rib around same size with 250 yamaha 4 stroke. if so what prop do you have on and what you gettin out of it at what rpm? i'd be lookin for something for cruising with light loads, maybe 3 or 4people, at around 25, 30knots ,??any advice would be good
We have the250 Yam and cant recal details of props , but I recal a test done by Yamaha and Ribeye to work through best options, I have asked for a copy and will post it if I can get it. Cheers Ian

Here is the first bit, still waiting on next
10 Yamaha personnel from Yamaha Europe and UK spent 3 days at Dartmouth HQ testing propeller combinations. The objective was to maximise performance of the Ribeyes i.e. speed and fuel efficiency, by matching the best prop to engine. The Props on test were black stainless steel, aluminium, salt water, performance, reliance and Pro series. The preferred prop for the 785 powered by a Yamaha F250 was the Pro Series 23”. The 650 with F150 combination tested best with the Black Stainless Steel 19”. The best choice and best performing propeller for a Ribeye 600 with F115 was the Performance Series 18”. Finally the preferred prop for the 500 with F80 was the Aluminium 17”.

Here is the relevant link to prop tests
http://www.ribeye.co.uk/documents/Ribeye785F250.pdf
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Old 18 March 2010, 10:15   #7
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thank you Ian ,you are the man, thats some great info,
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