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22-05-2014, 08:41 PM
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#1
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Registered User
Join Date: May 2009
Posts: 496
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Tighting Props and loose nuts
Was down in Teignmouth last week and popped in to have a look around the lifeboat station. In the station they have a large rib with twin 115 or around that size Merc Outboards. I was walking round noticed shiny bits and wear marks on the prop washers on both engines. The prop nuts although has split pins in were wobbly with the fingers loose as were the washers completly loose so you cold turn the washers with your fingers.
I inquired as to why and was told that was how they are supposed to be and it stops the shafts shearing if they hit something submerged.
Has anyone heard of this before and how tight should pro nuts be???
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27-06-2014, 02:09 AM
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#2
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Registered User
Country: Ireland
Occupation: Burning Petrol
Interests: Boats & Bikes
Boat name: The Doc
Boat make: Ring 21C
Engines: Yam proV 200
Cruising area: River Shannon
Join Date: Jun 2014
Posts: 33
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Prop nut torque
Mmm, never heard of that one. Usually it's set to 80nm on the castle nut, this will be lower on smaller outboards say under 30hp 10-20nm and up to 135nm for props with a bush between the thrust washer and prop. I normally set to 80nm and re check after a few runs as the thrust washer seats further onto the shaft
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27-06-2014, 07:58 AM
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#3
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Registered User
Country: Ireland
Location: Dublin
Occupation: Boatbuilder
Boat make: Hydrostream V-king, 650SS OCR ,Ring 21, Ring 18, Phantom 18.
Engines: 300Hp Mercury 2.4, 130 Yamaha, Bridgeport EFI, XR6, Merc 200.
Cruising area: Malahide, Dublin
Join Date: May 2004
Location: Dublin
Posts: 1,803
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Can't see how it would stop the shafts shearing unless it puts less torque on the hub. But mercs don't usually have split puns or castle nuts so its sounds like its something they've done! There's probably some method to the madness!
On a side note, whatever I torqued the prop nut to on my sportcat it was always loose after a run.
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27-06-2014, 10:30 AM
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#4
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Registered User
Country: UK
Location: london
Occupation: Powerboat Skipper
Interests: Boats , bikes!
Boat name: Renegade
Boat make: GPV-RENEGADE
Engines: 150 HO etec
Cruising area: Thames, south coast, anywhere!
Join Date: Dec 2008
Location: london
Posts: 2,330
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that tells me the bush is not seated on the thrust washer and i have seen flo torque failure due to this
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07-08-2014, 12:52 PM
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#5
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Registered User
Join Date: Nov 2009
Posts: 33
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Hi Im a technician for the rnli the reason behind it is for a easy prop change at sea. If prop gets damaged whils out on a shout ;-)
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13-08-2014, 08:30 AM
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#6
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Aged Member
Country: UK
Location: HAMPSHIRE
Occupation: Safety Engineering
Boat name: Savannah
Boat make: Princess 415
Engines: Volvos
Cruising area: SOLENT
Join Date: Oct 2004
Location: HAMPSHIRE
Posts: 779
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I used to use a Terry pin (bit like a large nappy pin) the same diameter as the split pin would be...that and a floating prop nut wrench would still give you a quick prop change at sea....did it several times when prop testing without the need to keep going back on the trailer.
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