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Old 10 April 2008, 17:02   #1
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4.50 Metre Rib-x 60hp Mercury What prop?

Can anyone recomend a prop for my outfit?

Often runnig with two to three adults in it.

I have a 4.5 meter centre console rib, it has a 2 stroke 3 cylinder mercury outboard with currently a 14 pitch prop.

It seem to rev too high to 6500 rpm???........... Mercury quote 5500 rpm max.

Current prop is 73138A4OP14 (14 Pitch)


Does anyone have a recomendation for a prop?

Does anyone have a spare prop for sale?

Many thanks

Chris
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Old 10 April 2008, 17:11   #2
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As a general rule of thumb a 2" change in pitch will have a 200 RPM change. i.e up in pitch down in RPM.
Hope thatb helps

By the way Welcome to the Forum
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Old 10 April 2008, 19:22   #3
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Odd question but are you sure your revcounter is reading right?
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Old 12 April 2008, 13:58   #4
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Old 12 April 2008, 18:48   #5
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Quote:
Originally Posted by ashbypower View Post
As a general rule of thumb a 2" change in pitch will have a 200 RPM change. i.e up in pitch down in RPM.
Hope thatb helps

By the way Welcome to the Forum
To be honest, I don't think that's correct, the rule of thumb: 1" higher pitch = 200 RPM less. So 2" pitch higher will result in a loss of 400 RPM. I think it's reasonable to test a 19" pitch prop on the 60hp merc.
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Old 14 April 2008, 15:52   #6
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19 pitch prop?

Thansk for the advice everyone...........

The highest pitch mercury make for my engine is a 19 pitch, if we base 1 pitch on 200 rpm will it be enought to bring the revs down to a safe limit? 1000 rpm to high ?

Has anyone else got a 4.5 meter with a 60hp on it?

Many thanks for the advice........


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Originally Posted by reinier View Post
To be honest, I don't think that's correct, the rule of thumb: 1" higher pitch = 200 RPM less. So 2" pitch higher will result in a loss of 400 RPM. I think it's reasonable to test a 19" pitch prop on the 60hp merc.
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Old 14 April 2008, 18:43   #7
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Yeah, from 14" to 19" pitch = 5" pitch increase, mutiplied by 200rpm = 1000rpm decrease... If you use a stainless steel prop your rpm's will fall another 100 or maybe 200rpm. If you use a fourblade prop it will decrease the rpm's also with 100 or 200rpm.

If the 6500rpm is with a 14" aluminium prop, I suggest testing a 3 blade S/S 19" pitch prop.
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Old 15 April 2008, 13:28   #8
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Your prop number 73138A40P14 is the standard Black Max prop that is put on a 60hp Mercury so are you sure the rev counter is accurate. Get a dealer to rig your engine to his laptop with the diagnostic program running and he will be able to tell you the exact revs the engine has been doing.
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Old 16 April 2008, 15:55   #9
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Rev counter problem

Thanks for your advice, I took out the rev counter today and found it to be sqithed in the wrong position, eg for the wrong number of cylinders........ Havent been able to retest it yet. Then will need to check the prop again. A rule to never trust somelse to do things right.........The guy I bought it from installed the rev counter!!!

Will it be reading double?

Quote:
Originally Posted by Red Fox View Post
Your prop number 73138A40P14 is the standard Black Max prop that is put on a 60hp Mercury so are you sure the rev counter is accurate. Get a dealer to rig your engine to his laptop with the diagnostic program running and he will be able to tell you the exact revs the engine has been doing.
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Old 17 April 2008, 16:44   #10
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Prop selection

I have a Tornado 5mtr with a 60hp 2 str that I run with a 13p and a 14p Alu Merc prop on. Usually I run with the 13p as I take up to 4 divers on it. However when I am running with the family and just pottering about I use the 14p, I would have thought that the 14p is probably about right for general use and then perhaps a 15p for light use. I use Alu as I have heard the odd horror story about SS props damaging the gear box if you hit the bottom.
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