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Contra-Rotating Props?


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I would be surprised to see this picked up by OEMs.  If fuel economy is the primary reason for this, I don't see it paying for itself quickly.  Also since it is below the water line I wonder what the maintenance will be?  Gear oil changes based on hours/calendar just like sterndrives?

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For 3 event application, does not seem a good fit.  Added cost and the fact that for slalom, some side torque helps keep a straight path and added transom weight hurts wake in addition to maintenance probably makes it an idea that is not good for the 3 event boat.  And furthermore, it eliminates the opportunity for Bu and Craft owners to gripe about CC reverse pull direction. :whistle:

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2 hours ago, ahopkinsTXi said:

Guys, this is designed for inboards that go in 30'+ boats. It's for efficiency. Helps provide more torque with less power. 

...I agree, but the press release says it was initially designed for the tow boat market.  They're dreaming. 

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I think it’s a great idea, especially for surfing.  More prop surface area without changing the angle of the prop shaft and no prop torque would be great. The ability to back straight up in a boat with thrusters would make it much easier to drive.  

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Many years ago I was looking at an I/O with contra rotating props. I looked into the price of props, a set of duo props was something like 4 times the price of a single.  Might end up being the case with this also.

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23 minutes ago, MadMan said:

Many years ago I was looking at an I/O with contra rotating props. I looked into the price of props, a set of duo props was something like 4 times the price of a single.  Might end up being the case with this also.

MerCruiser Bravo3 are about twice as expensive as a single prop (makes sense, as there are two props).  I had the B3 outdrive on my last boat.  Better hole shot.  Eliminated any list at speed.  More maneuverable around docks.  Less wander at idle.  Well worth the potential increase in cost.

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13 hours ago, formulaben said:

...I agree, but the press release says it was initially designed for the tow boat market.  They're dreaming. 

I know. Like you said I think they are dreaming. Maybe we are wrong but I don't see this ever being applied to our type of tow boats. Even the monster wake boats out there now  

@oldjeep what pictures are you referring to? I see one of the proposed driave train and one of a hull rendering that looks more like a 25-27' cruiser hull than any wake hull I've seen. 

 

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4 hours ago, ahopkinsTXi said:

I know. Like you said I think they are dreaming. Maybe we are wrong but I don't see this ever being applied to our type of tow boats. Even the monster wake boats out there now  

@oldjeep what pictures are you referring to? I see one of the proposed driave train and one of a hull rendering that looks more like a 25-27' cruiser hull than any wake hull I've seen. 

 

This one - which is a v-drive and looks to be maybe a 21 ft boat if the engine is to scale

 

zf-project-disruption2.jpg

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21 minutes ago, oldjeep said:

This one - which is a v-drive and looks to be maybe a 21 ft boat if the engine is to scale

 

zf-project-disruption2.jpg

Yeah that's probably true. I guess I didn't look at that picture very hard lol. 

Looks like that gear box in the skeg would add another 12-16" to the draft. That will be good ... :blush: 

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4 minutes ago, ahopkinsTXi said:

Yeah that's probably true. I guess I didn't look at that picture very hard lol. 

Looks like that gear box in the skeg would add another 12-16" to the draft. That will be good ... :blush: 

And make tracking/steering weird.  Not sure what the impact of that big fixed skeg being that far back would be.  

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