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Old 21 November 2012, 17:25   #1
nob
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prop

oh god i think i've cocked up i've just been looking at my prop, like you do, and it looks kinda small compared to my mates! my engine is a 1993 merc 50hp 2 stroke but it came off a 19ft orkney longliner so is the prop going to be ok on a 4m searider, my mates boat is 4.5 mtr with a 40 hp evinrude 2 stroke and the prop looks bigger, - what sort of size should i be looking at on the searider: sorry for all the questions but i haven't put it in the water yet and dont want the motor to over rev or do anything else horrible if getting the right prop will stop this, many thanks, nob
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Old 21 November 2012, 17:28   #2
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try it first
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Old 21 November 2012, 17:32   #3
nob
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yeah you're right but how will i know if its over revving, is it just by sound/feel?
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Old 21 November 2012, 17:40   #4
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Quote:
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oh god i think i've cocked up i've just been looking at my prop, like you do, and it looks kinda small compared to my mates! many thanks, nob
Well I never... looking at your "handle" I would have thought that it would be much bigger than yer mates nob.
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Old 21 November 2012, 17:42   #5
nob
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well yeah, obviously, but we're talking props here honest
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Old 21 November 2012, 17:48   #6
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You probably need a 14" or 15" pitch prop with that motor on an SR4. It may have been propped wrongly for the Orkney, so don't assume anything.

Your mate's Ermintrood has a lower ratio gearbox, so will naturally run a higher pitch prop than your Merc.
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Old 21 November 2012, 17:52   #7
nob
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cheers downhill, roughly what would that measure across the face of the prop, i cant see any markings on it ?
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Old 21 November 2012, 17:56   #8
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well yeah, obviously, but we're talking props here honest
I believe you honest
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Old 21 November 2012, 17:57   #9
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yeah you're right but how will i know if its over revving, is it just by sound/feel?
Chances are you'll experience emptiness towards the end of your throttle travel, a bit like "blowing in the wind".........much ado about nothing. ( simply put the prop is too small )
The opp side to this is the engine throbbing and sounding "gluggy" and taking an age to spin up. ( in simple terms the prop is too big here )
However it's not a size thing........there is pitch, diameter and slip.
Not an easy thing to work out even for experienced users. You need a prop specialist. Cheapest way out, if you find the right guy/gall.
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Old 21 November 2012, 17:59   #10
nob
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oh bugger, now i've got to ask his missus whos is biggest
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