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Old 21-08-2017, 11:43   #1
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Which fixed 3 blade prop for my Yanmar 2GMF20 powered Alberg 30?

Don't ask why but mine fell off :-( Boat went on the hard today and realized I have no idea what prop they used when they repowered the boat. Anyone know? I'm going to email the Alberg 30 list too but thought I'd throw it out there to the smart folks of CF too. Time is of the essence.
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Old 21-08-2017, 12:44   #2
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Re: Which fixed 3 blade prop for my Yanmar 2GMF20 powered Alberg 30?

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Originally Posted by Alberg30Shill View Post
Don't ask why but mine fell off :-( Boat went on the hard today and realized I have no idea what prop they used when they repowered the boat. Anyone know? I'm going to email the Alberg 30 list too but thought I'd throw it out there to the smart folks of CF too. Time is of the essence.

Not just what size prop, but look at what direction the prop would turn in forward...left hand or right hand.....it makes a big difference....and as for the alberg 30, I'd suggest a folding prop like the bruntons autoprop as you would have less drag while sailing, and better fuel usage under power.
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Old 21-08-2017, 13:03   #3
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Re: Which fixed 3 blade prop for my Yanmar 2GMF20 powered Alberg 30?

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Originally Posted by Alberg30Shill View Post
Don't ask why but mine fell off :-( Boat went on the hard today and realized I have no idea what prop they used when they repowered the boat. Anyone know? I'm going to email the Alberg 30 list too but thought I'd throw it out there to the smart folks of CF too. Time is of the essence.
When you speak to a propeller supplier you will need the following information:
1) what is the transmission ratio? There were different ones available and
2) what diameter propeller can you fit?
With this information plus the Alberg 30 specs the prop supplier might actually provide the correct propeller.
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Old 21-08-2017, 13:04   #4
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Re: Which fixed 3 blade prop for my Yanmar 2GMF20 powered Alberg 30?

Yep, get a modern prop. Now is your opportunity. Check out Max prop. Less prop walk and more reverse thrust.
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Old 22-08-2017, 03:31   #5
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Re: Which fixed 3 blade prop for my Yanmar 2GMF20 powered Alberg 30?

For a pretty good idea of what you want go on line and fill in the details, they are actually very close to being right on!

https://www.vicprop.com/calculator.htm

Propeller Calculator / Prop Calculator
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Old 22-08-2017, 06:09   #6
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Re: Which fixed 3 blade prop for my Yanmar 2GMF20 powered Alberg 30?

As stated there are several unknown factors which need to be known to make a correct selection. Here's my take on your boat:

- the prop is in an aperture so the repower was done with a 2.21:1 reduction ratio so as to require the smallest prop

With this ratio the ideal prop is a 14.7 X 7.8 X 3, but probably a 14 X 8.5 X 3 was fitted if it can fit in the aperture with adequate tip clearance (approx. 15%).

If that's too big go to a 13 X 8.5 X 3, and if that's too big you will have to continue down in diameter and up in pitch about an inch at a time on each.

Once below 13 " diameter, efficiency will begin to suffer as blade area gets too small. Your engine will use a right hand prop.

DougR
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Old 22-08-2017, 17:38   #7
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Re: Which fixed 3 blade prop for my Yanmar 2GMF20 powered Alberg 30?

Save your money, two blade,fixed, spent money, go crazy...
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Old 22-08-2017, 18:24   #8
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Re: Which fixed 3 blade prop for my Yanmar 2GMF20 powered Alberg 30?

A two blade fixed prop is indeed less expensive than a three blade, but it comes with two problems:

1. A two blade prop has 1/3 less blade area than a three blade prop of the same diameter, so to get adequate blade area to absorb the power, you will have to increase the diameter over that of a three blade. That might not be possible within the existing aperture and still retain adequate tip clearance.

2. When a two blade prop is running in an aperture and the blades pass behind the dead wood area of the hull, both blades hit static water at the same time inducing a torque/ vibration into the prop shaft. With a three blade prop only one blade hits the dead wood area at a time, so the twist and vibration introduced into the shaft is less severe.

DougR
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