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Old 24 September 2002, 09:36   #11
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I have a tornado 4.8 with a yamaha 60 and it seems to have around the same top speed whether I have 1,2,3,4 or even 5 people on board! accelaration differs but not too much. I wouldn't think that 20cm and 10hp could make a massive difference, noticable but hardly worth worrying over!
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Old 24 September 2002, 09:53   #12
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50HP certainly won't be underpowered but it obviously won't be as nippy as if you had a 75 or 90HP

I have a 60HP on my 4.7m RIB. I get a max speed of 33kts with 1-2 people and that only drops to 31kts with 8 people on board (I would not recommend 8 people in a 4.7m RIB). Prop choice will be quite important. The prop which came with the boat gave me much better top speeds but wan't as good in rough weather/water sports.

Daniel (the 2nd) Loughlin
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Old 24 September 2002, 11:34   #13
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Hi Brian

Quote:
What I don't remember seeing, however, was Keith's calculation of power/weight ratio AFTER taking Quicksilvers crew into account !!!
Difficult one that Brian. It depends whether I'm out in the boat before or after dinner!

Keith (these brackets seem to be catching on) Hart
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Old 24 September 2002, 11:54   #14
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Keith

Sorry to point this out Keith me old mate but do you really think that in the grand scheme of things the amount of dinner you've had makes a difference??
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Old 24 September 2002, 11:57   #15
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Alan

If you'd ever seen the amount of dinner that I eat, you wouldn't be asking that question.

Keith (burp) Hart
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Old 24 September 2002, 11:59   #16
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Should the brackets thus read....

Keith (He can eat his own bodyweight) Hart?



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Old 24 September 2002, 13:50   #17
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Conclusion

50 Hp should be ok for general sunbathing use !

(given my current 15 hp gets 4 of us on the plane in the little avon and I reckon will do about 25 mph, I reckon 50 hp should shift us )

Do I assume correctly that this 50 HP would on the flip side offer better fuel consumption than say I was running a bigger 75 on the same boat ???

Keith you realise I only sold my 6 metre rib and bought this 3.1 metre Avon just to capture your award of smallest boat on rib.net !!!
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Old 24 September 2002, 14:12   #18
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Try the link below. For $20 US you will be given a complete analysis of what to expect. There is a sample report on the site to see if it is what you are looking for. You get unlimited on line reports for 20 days, maybe you could do some for others for a beer.

http://www.propworks.com/becomeamem.htm

Pete
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