Does it matter how duoprops are positioned on the drive shaft?

[golf101]

I'm putting back on duoprops for the first time on a Volvo Penta sterndrive. The Volvo manual does not indicate that it matters how the rear prop blades are positioned with regard to the front prop. Just double checking to find out if there is any preferred position for the blades of the rear prop, such as whether the blades should be aligned to fill the "gaps" in the front prop blades (i.e., so that the blades don't line up with the front prop blades).

 

[golf101]

Re: Does it matter how duoprops are positioned on the drive shaft?

You can ignore this post. I found an old thread from 2006 that addresses it.

(Moderators: How do I delete a post? The FAQs say I can do so by clicking on "Edit" on my post, but, after I did that, I didn't see any way to delete it.)

 

[Maclin]

Re: Does it matter how duoprops are positioned on the drive shaft?

Volvo seems to have no position on this, and there is no key way or other mark to go by on the props or the shafts. My research found some reasons for clocking them so both blades do not pass under the anit-cav plate at the same time. There is no downside and it is simple to do. Put the big prop on with a blade straight down, and the small prop on with one blade straight up. They turn at the same rpm so they will always pass like that under the plate.


Here is a sample of what I have found, there is more out there and one time I even found a Volvo tech that thought this made a difference, but this is a good microcosm of the debate...:

http://www.albemarleboatowners.com/forums/viewtopic.php?t=680&highlight=cavitation

I have experienced the prop burning from cavitation, clocking mine as described eliminated the problem.

 

[Maclin]

Re: Does it matter how duoprops are positioned on the drive shaft?

I must have been typing while you were looking.....!

 

[golf101]

Re: Does it matter how duoprops are positioned on the drive shaft?

Maclin: Thanks much for your response. You confirmed what I saw. Like you, I concluded that there is no harm to placing them in the positions relative to one another that you suggested, so I did so. I have not been able to get my boat back out, but will this weekend and will see how it compares to not having them aligned in this manner.