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Old 17 August 2008, 10:23   #1
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Suggested prop size for a 1997 90hp Yamaha autolube 2 stroke

Can anyone offer any ideas on the above question it would be greatly appreciated.
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Old 17 August 2008, 14:01   #2
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What boat is iti on?
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Old 17 August 2008, 14:57   #3
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And what will the boat be used for? How heavily loaded, etc.?
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Old 18 August 2008, 03:35   #4
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Sorry should have said

Its on an 18ft Wilson Flyer (sorry not a RIB) fishing boat that carries between 2 and 3 people. I recently changed to the yamaha from a 60hp evinrude vro. However the yamaha does not seem to give me any more speed than the evinrude did. At present the Yamaha has a 13.25 x 17 on it and was wondering if this was correct of not.
Any help received would be appreciated.
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Old 18 August 2008, 04:03   #5
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You need to check the RPM you are achieving with the engine at WOT (Full throttle) and also trimed out for maximum speed.

I am unsure what the target RPM is for that engine at full chat but I would have throught it would be towards 5,600 to 5,800 RPM.

I am assuming you have a rev counter?

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Old 18 August 2008, 04:22   #6
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How fast does it go at WOT and what RPM are you hitting?
Is the engine running ok and is the prop in good condition?
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Old 27 August 2008, 08:54   #7
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even without the RPM figure, it seems evident that 17" is too much, should you have the possibility to try a 15" shoulld give a solution
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Old 27 August 2008, 12:47   #8
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Max WOT rpm for that engine IIRC is 5500.

Try a 15".
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Old 29 August 2008, 03:38   #9
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Thanks for all the suggestions.

RPM seems to be around 4000 and top speed around 28mph. Will try a 15" prop and see if that cures the problem also have a mate coming down to clear out the carbs just in case.
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Old 08 September 2008, 09:40   #10
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Hi All

Changed the prop to a 15" and things have remained pretty much the same any ideas.

Many thanks
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