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Prop Indexing

I don't see the point, either, since props turn in opposite directions. Essentially the index and un-index (?) 3 times in each revolution. Was just a discussion on the dock one day ... :rolleyes:
 
The reason that can't tell you if it makes much difference, is because I have always indexed mine.

The theory is: we do not want any two given blades to pass near the 12:00 position simultaneously..... such as what this set is doing or is about to do.

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Apparently the water flow disturbance (caused by the vertical portion of the drive case), renders the propulsion less effective when two blades pass near each other at this position simultaneously.


This is what Volvo Penta prefers to see.
As the FWD propeller continues to rotate CCW, it's vertical blade will now be near the 10:00 O'clock position during the time that the AFT propeller vertical blade (rotating CW) reaches the 12:00 O'clock position.

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It's very simple to index them..... so why not?
Once indexed, they will remain indexed.


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Curmudgeon said:
........... only single blades at 12 ... :)
Click to expand...

When either is rotated, they will obviously change positions with one prop's blade at 12:00 O'clock, the other prop's blade at near 10:00 O'clock (or visa versa). But neither prop will have a blade at 12:00 O'clock at the same time.

IOW, any two blades from two oposite propellers are to NOT be at 12:00 O'clock simultaneously.

Here's what they should look like when indexed correctly.

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