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Old 07-09-2022, 08:20   #1
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Prop walk w/ counter-rotating props?

Son-in-law's new Cobalt R4 has Volvo-Penta V8 with counter-rotating props. As a sailor, I was expecting little to no prop walk with this arrangement, but I seem to be wrong. Only way to back straight out of hoist is to keep wheel all the way over to port as stern wants to swing to hard to starboard otherwise. Also seems to happen in bursts, like deep-V wander in reverse. (I should note that the drive is trimmed up substantially to minimize draft in the shallow water approaching the hoist.)


Help a powerboat rookie out: Am I missing something here? What's the best way to get into and out of a hoist (waterfront home located on a Great Lakes roadstead) with such severe prop walk?
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Old 07-09-2022, 08:30   #2
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Re: Prop walk w/ counter-rotating props?

Are you sure they are counter-rotating and not opposite handed props?
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Old 07-09-2022, 08:35   #3
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Re: Prop walk w/ counter-rotating props?

Boat has Volvo's "DuoProp" system, supposedly true counter-rotating in-line props.
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Old 07-09-2022, 08:37   #4
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Re: Prop walk w/ counter-rotating props?

How does it back with the drive all the way down?
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Old 07-09-2022, 08:38   #5
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Re: Prop walk w/ counter-rotating props?

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How does it back with the drive all the way down?

Essentially the same, played around for quite a while in deep water just to see.
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Old 07-09-2022, 08:46   #6
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Re: Prop walk w/ counter-rotating props?

Admittedly, I can't comment specifically on Volvo. However, I used to own a boat with a single Mercruiser Bravo III. This is a counter-rotating dual prop as well. On that boat there was ZERO prop walk.
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Old 07-09-2022, 08:47   #7
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Re: Prop walk w/ counter-rotating props?

Does that Volco use hubs? It could be possible that one of the hub is 'spun'. That could lead to a condition where one prop is biting properly and the other is not.
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Old 07-09-2022, 11:37   #8
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Re: Prop walk w/ counter-rotating props?

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Does that Volco use hubs? It could be possible that one of the hub is 'spun'. That could lead to a condition where one prop is biting properly and the other is not.

I thought about that, but A) the boat is brand new, and 2) acceleration going forward gives no indication that I'm missing one prop's participation which I would think you'd be able to feel. Thing takes off like a torpedo (says the sailor!).
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Old 07-09-2022, 11:43   #9
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Re: Prop walk w/ counter-rotating props?

Weird. My fathers boat has a duoprop outdrive. I was surprised at the control I had backing…of course I’m used to a full keel.
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