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Old 17-07-2007, 11:30   #1
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counter rotating props on a catamaran

I have ordered a new cat (a Leopard 40), and learned that both props turn the same direction. This should give double the prop walk. If they each turned in different directions, prop walk could be neutralized for cats (and twin screw powerboats).
Is there a way (simply) that a Yanmar saildrive can be made to turn in the opposite direction? Then, when I order the aftermarket folding props, I can get one right and one left hand. Any reason why I shouldn't do this?
Thanks.
Robert
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Old 17-07-2007, 11:40   #2
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It looks like they only make them go one direction CC. http://www.yanmar.com.au/marine/sail...ail_series.htm

You could give them a call. It may be a special order.

Prop walk usually occures when the prop is close to the surface with larger props. I'm not sure that a sail drive would cause you much trouble. On a Cat they are so far apart they hardly affect one another.
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Old 17-07-2007, 12:02   #3
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Thanks. That was the right site. For me, it is no longer an issue, since the SD20 saildrive for the 29HP Yanmar runs only one direction. I guess I will just order the folding props from the factory.
The larger saildrives (SD50) can run either direction, and wonder if the boat would run more efficiently with counter rotating props - saildrive or shaft.
Robert
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Old 17-07-2007, 12:16   #4
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I don't believe you will experience any ill effects from same rotation. The distance between shaft center lines is so far apart.
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Old 17-07-2007, 13:59   #5
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Prop walk is due to down angle of shaft/prop, NOT the fact that the prop is turning in the water. With the sail drive being horizontal, you won't experiance prop walk.
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Old 17-07-2007, 14:05   #6
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counter rotating props

I bought a 45' leopard with both props clockwise with shafts it didn't handle very good around docks I switched maxi props to one left and one right hand drive, switched controls also, now both props turn outboard ,handles alot better can walk it sideways port and starboard
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Old 17-07-2007, 16:38   #7
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We have a 38' Prout with 2 Volvo Sail drives both left hand rotation. Prop walk is negligible and with 2 screws so far apart, maneuvering in tight quarters is a joy. It's almost like playing a video game.

George
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Old 17-07-2007, 17:12   #8
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We have a Manta 40 with Volvo sail drives both same rotation. No prop walk issues. BTW, the Volvo saildrives work the same in both directions. You just need to change one prop and reverse the shift cable.

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Old 17-07-2007, 19:56   #9
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Quote:
Originally Posted by ub1
I bought a 45' leopard with both props clockwise with shafts it didn't handle very good around docks I switched maxi props to one left and one right hand drive, switched controls also, now both props turn outboard ,handles alot better can walk it sideways port and starboard
So are you running one motor in reverse full time now??

Are they electric or petro.

Or is the trany geared the same ratio both directions?
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Old 18-07-2007, 00:55   #10
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Twin drives working the same rotation seem to work OK. Twin drives working opposing rotations with the rotation outward, works very well. Twin drives with counter rotation inwards handles like a pig in mud.
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Old 02-09-2007, 05:03   #11
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Why do you think this is an issue? My Yanmars turn the same way, and it isn't an issue.

Enjoy the boat and don't worry about it.
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Old 02-09-2007, 07:39   #12
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never noticed any prop walk effect on our shaft driven props!
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