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Old 18 May 2013, 16:06   #1
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Yamaha 150 Prop size

The 150 on my Ribtec 655 is only getting 4100 RMP at WOT, the boat is plenty quick enough but something tells me I should be getting more than that. The only marking on the prop is, I think, 19m. Anyone have a similar set up and know what prop they're running?

Also, it has an stainless prop but I like the sacrificialness of aluminium, is this a bad ideal on an engine this size? I know I'll loose a little performance but I have some spare!
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Old 18 May 2013, 16:33   #2
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4100 is quite low.


I don't know if playing with the prop is going to find you the revs you are missing.
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Old 18 May 2013, 16:42   #3
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I've found this....

http://www.ribeye.co.uk/documents/Ribeye650F150_000.pdf

I'm getting 42 knots at full throttle which is kind of inline with the figures for the Ribeye they're testing with my prop, I was wondering if it could be the gauge but it's all digital.
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Old 18 May 2013, 16:44   #4
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I've found this....

http://www.ribeye.co.uk/documents/Ribeye650F150_000.pdf

I'm getting 42 knots at full throttle which is kind of inline with the figures for the Ribeye they're testing with my prop, I was wondering if it could be the gauge but it's all digital.
Has it always revved out at 4100?
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Old 18 May 2013, 16:45   #5
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Max RPM range on that is 5,000 - 6,000. The Yam spec sheet below shows 150hp at 5,500 rpm and I'm not sure your going to find your missing 1,400 rpm on pitch change alone ?

http://www.yamahaoutboards.com/outbo...specifications

www.BoatsandOutboards4Sale.co.uk
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Old 18 May 2013, 17:10   #6
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Thing is, going by the Ribeye data, at an RPM of 4.5k I should only be going 30 knots and I'm going much faster.



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Has it always revved out at 4100?
New boat
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Old 19 May 2013, 14:03   #7
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Don't discount a rev counter issue if you're getting that speed at what you think is 4100rpm!!
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Old 19 May 2013, 14:07   #8
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my Ribtec 655!
Congratulations!!!

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Old 19 May 2013, 14:13   #9
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Thanks Chris - No Merc though, sorry.

Starting to think it could be the gauge, might get my not sol local engineer to take a look next time I'm in the area.
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Old 19 May 2013, 21:37   #10
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Get hold of an automotive tune-up tach and bounce that against the installed tach. Dead simple; you need only 12V, Gnd, and an exposed spark plug wire to clip the inductive pickup around.

How long does it take your boat to plane? If it's not a long time, then your prop is probably not far enough out to cause that much rpm disparity.

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