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Twins counter rotating prop question

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volvo250

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twins-counter rotating prop se

twins-counter rotating prop setup Volvo 280 outdrives
What is the proper rotation? Currently port-counter clockwise and starboard-clockwise.
Does it matter?
 
"I am getting confused with th

"I am getting confused with this because of of props marked R (right) and L (left) and diagrams in manual. So should I swap the props on the outdrives and change rotation settings to make R -clockwise-port side? That would give me proper rotation counter clockwise on the starboard with L prop and port clockwise with R prop. . Is that the correct setup? Sorry if I sound confused, I am. Do I understand R and L prop rotation correctly? R should rotate clockwise and L counter? Thanks again for your valuable help,"
 
"Rick M, According to Volvo,

"Rick M, According to Volvo, yes.... it does matter!
Look at page 76 of the OEM Volvo manual #7731624B.
Port side = LH prop (lower driven gear same as DP)
Stbd side = RH prop (upper driven gear)

When I had sp drives, that is how I had mine set up. (I now have twin DPs)

Look at page 77 for drive alignment regarding toe-in adjustment procedure.
Make sure that you part the drives (fully apposed) when checking this measurement.

The trick is setting your torque tabs/trim fins since you now have two counter rotating props possibly fighting one another.
While some say that this steering torque is countered by counter rotation props, there is still plently of torque being applied to your steering components. (torque that you may not feel at the helm wheel)
Try to avoid letting the steering system continuously fight this prop wash torque.
It is not easy to get this correct!

."
 
"El and Ricardo, thanks for yo

"El and Ricardo, thanks for your replies. Is it me or do you fellows disagree? At least I feel better about being confused. Unfortunately the manual is at the boat and I am not, so I am unable to confirm which specific manual I was looking at. I will look at it again, but the seemingly contradictory diagrams are what got me confused in the first place. Any further discussion on which way is best?
Thanks."
 
"Thanks,
So they are on corre

"Thanks,
So they are on correct.
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I really appreciate the help. This is a great service you provide."
 
"Eduardo, with all the good th

"Eduardo, with all the good that you contribute to this forum, I think an occasional S/U is OK.... but that's it for the year! Only one!
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Rick, I am certainly not an expert on this, however, I think that this has much to do with the way in which the water is coming from with under the hull at the deepest portion of the V. Apparently, there is a thrust gain if running in this configuration.
I do know that there is a significant difference in prop wash/thrust when a blade is passing at 12:00 'O'clock position (water coming past the bullet portion of the drive) as apposed to the 6:00 'O'clock position.
However, I can't seem to tie this in with a RH/LH twin drive discussion.
I just trust the V/P engineers!"
 
"El:
I did a few of that &#39

"El:
I did a few of that 'set-up's', but for a special reason. It was all on 'super fast' rigs, and the intention was to give the props a 'spin-off' at start. You have a parallel in the relief holes in the raker props. I'm not able to see if the props at the pick have the same holes, but I suspect no.
Running stb = counter clock and port = clock wise on a 280/290 SP set-up have never been a success. However if You have an extreme deep V, above 25' it might be a solution, but that again may depend on props used. For a std set up and installation, I would go the conventional way. The toe-in factor is sometimes the most difficult one, and any play in drive suspension and steering systems might mess it up a bit."
 
"Ricardo & Morten, again I

"Ricardo & Morten, again I admit this is a BIG screw-up on my side. There are applications for inward propeller rotation, but they do normally apply to large ships, not to small craft. In short, I did not have around the reference material that I would normally check when in doubt or in case of brain farts, and I got mixed-up. Next time I will triple check before shooting.
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"
 
"Well, looks like it's you

"Well, looks like it's your turn in the barrel this week, Eduardo. Mine next week! LOL

Hey, quit apologizing.... we all make a boo boo now and then."
 
Ran across a paper once which

Ran across a paper once which indicated that "inward turning" props (relative to one another) on dual installations where the drives/props were CLOSE would solve a cavitation problem due to outward turning props causing ventilation in the area between the drives....
For other apps... outward turning.
 
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