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Message |
    
mv_pagu
New member
Username: mv_pagu
Post Number: 1
Registered: 05-2012
| | Posted on Wednesday, May 30, 2012 - 03:42 am: | 
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I'm re-powering a boat and want to be sure I have a correct understanding of Direction of Rotation before committing to the new engine and transmission. The old engine: if you face if from the bow, the fly wheel turns clock-wise. Am I correct in understanding that this is what's known as Right Hand rotation? And that the prop, if faced from the stern would like-wise rotate clock-wise? |
johnoxley
Senior Member
Username: johnoxley
Post Number: 60
Registered: 04-2010
| | Posted on Wednesday, May 30, 2012 - 07:13 am: |
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Think you have a LH prop - hold out your left hand with thumb towards your face and your fingers in a grip position - this will show shaft rotation for a left hand prop.
Practise above a simple water tap - right hand - thumb up - fingers curled in grip position show rotation to open tap, hence a right hand screw thread.
Next the final test - find a Chrysler or Dodge car - use your left hand to give the rotation direction to remove and replace the LH wheel nuts. Then vice versa - use your right hand to give the rotation for the RHS wheel nuts. |
jb_castagnos
Senior Member
Username: jb_castagnos
Post Number: 691
Registered: 07-2002
| | Posted on Wednesday, May 30, 2012 - 01:46 pm: |
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If the propeller is on a table in front of you, you can pick up a left hand prop with your left hand, a RH prop with your right hand. |
richardday
Senior Member
Username: richardday
Post Number: 1005
Registered: 11-2003
| | Posted on Wednesday, May 30, 2012 - 02:38 pm: |
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If your engine flywheel turn clockwise facing toward the prop drive shaft and the prop drive shaft turns the same the prop should be left hand. Some reduction gears can change prop shaft rotation direction so make sure. |
mv_pagu
New member
Username: mv_pagu
Post Number: 2
Registered: 05-2012
| | Posted on Wednesday, May 30, 2012 - 03:33 pm: |
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Many thanks for the replies. I've got to be honest though. I'm now even more confused. The previous engine (one I'm replacing) was a Yanmar, & I understand all Yanmars are RH. So the existing prop should be machined for RH rotation, right? But from the replies suggest is LH? I've attached a pic of the prop (which is in the Solomon Islands), which to my limited knowledge looks like it should rotate clockwise (when viewed from behind) to drive fwd? Right? |
adsum
Advanced Member
Username: adsum
Post Number: 36
Registered: 01-2008
| | Posted on Wednesday, May 30, 2012 - 04:24 pm: |
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I think it is a RH prop that rotates clockwise when moving fwd. |
johnoxley
Senior Member
Username: johnoxley
Post Number: 61
Registered: 04-2010
| | Posted on Wednesday, May 30, 2012 - 05:16 pm: |
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Agreed picture shows a right hand prop. (The overhang seems extreme and would not be allowed by local authorities here. Ours would ask for a longer support bearing.) |
nobby
New member
Username: nobby
Post Number: 3
Registered: 12-2005
| | Posted on Wednesday, May 30, 2012 - 10:10 pm: |
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First off with any marine engine installation do not go by generalisations such as all Yanmars are right handed because they are not. Go by what you actually have in the vessel. Next engine rotation is based on looking at the flywheel i.e. looking from the stern of the boat. CCW is Left Handed and is the the norm, CW is Right handed and is not the norm and is usually done for the Stbd engine of a twin screw vessel.
So as per your first post based on CW rotation from the front you have a Left Handed engine (CCW looking at the flywheel) no surprise their for a single engine. Based on your picture you have a Right Handed CW prop as you described in the first post also. No surprise their also Yanmar do supply Right Handed transmissions on left handed engines.
So to summise you need to create a right handed rotation at the propshaft. Nowadays right handed engines are not really being done, manufacturers are creating the right hand via the transmission. You have a few options based on installing a new left handed engine.
Keep your existing gearbox possibly rebuild it and just change the engine.
Install a new right handed output transmission also.
If you somehow have to go with a new left handed output transmission then change the prop. |
mv_pagu
New member
Username: mv_pagu
Post Number: 3
Registered: 05-2012
| | Posted on Wednesday, May 30, 2012 - 11:47 pm: |
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A very informative and helpful response! Thanks very much Nobby. Appreciated. |
