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Old 26 March 2005, 03:34   #1
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To "Turn" a Prop!

Recently purchased a new Alloy Mercury prop on Ebay and tried to fit it yesterday. Went on OK but as I turned it the flange that sits inside the gearbox housing was just touching (in one place).

Question: Is there anything wrong with turning the diameter of this flange down a bit, say 2mm off the diameter?

Andy
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Old 26 March 2005, 05:49   #2
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You may need a different thrust washer?
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Originally Posted by Zippy
When a boat looks that good who needs tubes!!!
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Old 26 March 2005, 05:57   #3
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Thrust washer wouldn't help Cookee, it's the diameter and not the lip that I'm having a problem with. It only just touches and doesn't stop the prop from being rotated. It seems that the flange of the prop is very slightly off centre from the hub, quite a common fault of mass produced propellers I belive.

Maybe Julie could help on this one?
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Old 26 March 2005, 08:27   #4
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If it's touching in only one place, something is out of true.

If it is touching the gearcase in one place then the case is out of true. If the contact point is on the prop and as it rotates it wipes the inside edge of the casing then the prop or thrust washer is out of true. However, whilst skimming a wee bit off will be fine, the prop will be out of balance because it is running off centre in the first place.

Could it have taken a knock and the rear edge be distorted. If so, you may get it back into shape by careful use of a hammer. Seriously.

Generally, you do not want to make the space between the prop and the case bigger than necessary because it will let too much exhaust out into the prop blades.
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Old 26 March 2005, 08:49   #5
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If it's such a small amount of interferance that you can turn it with ease, it can only be a thou or two, just file high point off!
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Old 26 March 2005, 12:42   #6
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Yeh, but it's going to be off by the clearance which should exist plus the couple of thou.
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Old 26 March 2005, 14:18   #7
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Keep it real, it's an ali prop on a 60 merc!
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Old 26 March 2005, 15:55   #8
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Old 26 March 2005, 20:24   #9
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Thanks guys, I think the prop and the casing is a little bit out! Nothing I can do for the casing, but will take the prop into work and measure the runout with a DTI to determine if it's taken a knock or if it's at the hub. The prop has never been used but it could have taken a knock though. Only really wanted to know if it was OK to turn some "meat" off the lip, and I think you guys have answered that.


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Old 27 March 2005, 08:20   #10
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Quote:
Originally Posted by Jonny Fuller
Keep it real, it's an ali prop on a 60 merc!
My appologies, a 90 Merc.

It'll be fine if you turn a bit off, it really aint Johnny-rocket science, and if you remove a small amount of material from one side to get the desired clearance, with the hub being less than 4" dia, and made of a lightweight material, I don't think 'ballance' will be an issue at all.

Think how many props you see with huge chunks missing from the blade extremeties, which are on a greater radius, and it has to be fairy bad to cause any noticable vibration.
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