Counter Rotation Motors

[MouseDog]

I've seen on some boats that you will have two motors, one's prop turns clockwise, the other anti-clockwise, now my question.

Does the "unconventional" motor cost more than the normal one???  What about spares/props etc, do they cost more than normal???  Also, what are the benefits of having two motors like this instead of two "normal" motors???

 

[tkei]

Costs, i have no idea.
The idea behing counter rotation is that the torque of 2 motors with same direction rotation props will actually cause the boat to "twist" to starboars as the props pull through the water.
With counter rotation, the torque levels out the boat as the boat is being equally "pulled" both ways by the props.
Usually iys only in higher HP motors that you find this Ie 130 and above, as the issue is not as bad on smaller HP.
If you have ever ramped over a wave with taps full, you can feel how the props cause the boat to twist to starboard. Havnt tried with counter rotation, but should counter it.

I not sure if this makes sence, but that my understanding of it.

 

[Bliksem]

MouseDog wrote:

I've seen on some boats that you will have two motors, one's prop turns clockwise, the other anti-clockwise, now my question.

Does the "unconventional" motor cost more than the normal one???  What about spares/props etc, do they cost more than normal???  Also, what are the benefits of having two motors like this instead of two "normal" motors???

"Prop walk" is eliminated, thereby improving performance and reducing steering effort when swinging "large" props

 

[Rory]

think it helps on monohulls with motors closely mounted does not through "bad water" into the other motor and give a little bow lift i have heard.

 

[neilg]

cost is about the same, in most cases the Counter box parts is actually a tad cheaper

not found on Smaller motors, normally 150HP and bigger.