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Old 18 February 2021, 05:45   #1
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Country: UK - England
Town: London
Boat name: 154
Make: Avon
Length: 3m +
Engine: Mercury 7.5 lightnin
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Calibrating unused propeller - does it matter?

Iíve pick up a new looking 9/14 x 10 1/2 - J for my mariner 15.
It has some slight flat spots on two of the blades (shown in the pictures - No 1 and 2 have it and 3 is good)

Will these affect performance of it at all ? If so how can I refine it in a diy way?

I thought if I had the lower unit in a fixed vertical position and then introduced a file or sandpaper on a block, then this would hone it.

Is there a system and procedures for doing this yourself?

Thanks for any pointer on this.Click image for larger version

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Old 18 February 2021, 07:06   #2
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Country: UK - England
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Boat name: Nimrod II
Make: Aerotec 380
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Engine: Yamaha 15Hp 2-stroke
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Ideally you never remove material from a prop... hammering dings out is the way as it retains the weight of the blade. But it's very common to see blades like yours that look to have been cleaned up with a file and painted at some time.

I've see loads worse so would see how it runs as is... but yes in theory you could make up some indicator of dimension as it's turned on the OB and file the blades to match. Without the equipment of a prop shop I'd not bother though.

Did you want to pitch up to a 10.5"? They usually run great on a 9" with most SIBs.
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Old 19 February 2021, 18:03   #3
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Country: UK - England
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Boat name: 154
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Engine: Mercury 7.5 lightnin
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Quote:
Originally Posted by Fenlander View Post
Ideally you never remove material from a prop... hammering dings out is the way as it retains the weight of the blade. But it's very common to see blades like yours that look to have been cleaned up with a file and painted at some time.

I've see loads worse so would see how it runs as is... but yes in theory you could make up some indicator of dimension as it's turned on the OB and file the blades to match. Without the equipment of a prop shop I'd not bother though.

Did you want to pitch up to a 10.5"? They usually run great on a 9" with most SIBs.


Thanks Fenlander
I did by it cheap online and thought it was a bit old but mint unused condition but I see your point about such things possibly being give the treatment.

I learned that the J1 is more refined in someways than this J type. What is that difference in performance?
Is it worth me lightly filing a sanding the positive side to form a better cup edge?
The reason I bought the 10 Ĺ was because the original manual for these 1977 - 81 15 c yam/ mariner 2 stroke states you should use a 9 ľ x 12. So I compromised with this as the existing one on there is a mashed up 9 ľ x 9 Ĺ.

This combo will be pushing an aged 4.5 m zodiac sport sib pvc I presume with wood deck ( which I hope to change to an Ali one if I get any flags for a secondhand set out there.)
There is also the old Avon 4m sport with wood deck but this is the heavier Hypolon material.

Do you think these are a good combo or a little stretching for the 15c to perform well?
Any tips where to tweak would be always welcome.

Dai
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