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Old 09 May 2007, 05:15   #1
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Country: UK - England
Town: Mevagissy
Boat name: Olli
Make: Ribeye
Length: 6m +
Engine: Yamaha 115 Outboard
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Posts: 13
Disappointing Performance

Hi All,

This is my first season with my own RIB, it's a Ribeye 600 Playtime with a Yamaha F115 four stroke with a standard 19" alloy prop.

I'm really dissapointed with it's performance, it gets up on the plane nice and quickly but it's top speed is rubbish and I don't seem to be hitting my max revs.

The best speed I've had out of her was 36 knts at 5300 rpm that was on dead flat waters with the tide 2 up and 3/4's tank of fuel (70 litres or so) Most of the time I only get 31 knts WOT at 5000 rpm.

I was really hoping to see at least 40 knts out of her, am I expecting to much? Would a stainless steel prop make much of a difference?

Any feedback, much appreciated.

Christian
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Old 09 May 2007, 06:19   #2
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Make: Scorpion
Length: 8m +
Engine: 300 Verado
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If you are not hitting max rpm then you will not hit max speed, sounds like you need to re-prop to achieve a higher speed.
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Old 09 May 2007, 06:37   #3
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19" is a fair size prop, max rpm for your engine is 6000 so you could try a 17". The rule of thumb is you gain around 300rpm for every 1" of pitch you lose. Or you could try an 18" and maybe raise the motor up on the transom. Depends on where it's sitting at the moment. Your probably looking for the cavitation plate to be around 1" above the keel.
Best thing is to beg, borrow (not steal!) whatever props you can find and see what works. Sounds to me like you've definately got more to come though
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Old 09 May 2007, 06:50   #4
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Country: Australia
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Top speed is all about trimming the front up.My 5m Gemini with 90hp Mercury nose trimmed down does 35mph. Trim the nose up does 55mph balancing on its tail.It feels like releasing a handbrake on the car.
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Old 09 May 2007, 07:00   #5
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all about trim I suspect. get it onto the plane trimmed down and then trim up on flat water for max speed. Use the trim up in short prods of the switch and get the feel of whats happening to the boat thru your feet. Limit of trim being that the prop will ventilate(suck air) and the motor will over rev or the boat will become unstable and chine walk ( shake its head from side to side and generally become scary). answer is of course to trim back down a tad, the question of trim in other than flat water is another matter of course. Its surprising how many folk who come on courses that have had boats for years think that the trim switch is an on/off thing.
Then again of course you may have the trim all sorted out and its sommat else in which case kindly disregard the rabbitting on of this post
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Old 09 May 2007, 07:01   #6
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ooops sorry Mr Surfer - our posts crossed in the post somewhere
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Old 09 May 2007, 08:39   #7
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Country: UK - England
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Boat name: Olli
Make: Ribeye
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Engine: Yamaha 115 Outboard
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Posts: 13
Hi again,

Thanks for the posts back, I'll have a word with Rock Marine (the people who built it) and see if I can get a selection of props to try out. The max speed I've had on the boat is with the engine fully trimmed.

Thanks again for the feedback

Christian
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Old 09 May 2007, 09:01   #8
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re rib eye

i am supprised no other ribeye owners have responded to this thread as this i believe is a popular set up eg 600 plus yam115

Andy
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Old 09 May 2007, 10:38   #9
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more speed

Buy a jackplate.
Then you can raise your engine more and your prop is working in cleaner water.
the cavitation plate can be about 3 inch above the botom of your boat.
A lot of people will probably tell you that it is to high but just try it, you will see.
Most engines are mounted much to low.
And the engine should be mounted about 1 inch to starboard (because of the wheel effect of your prop).
then install a good hydraulic steering set like seastar pro.
you will see it reduces a lot of the chinewalking.
and off course a good prop will do a lot.
For me the tempest plus from mercury does the trick. (lots of bow lift)

good luck and sorry for my poor language.
i am just a stupid dutchman who likes to race.
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Old 09 May 2007, 15:23   #10
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Niels
Don,t apologise !If I could speak Dutch or any other language as well as you speak(write ) English I would be delighted !!
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