silversupercoupe

Anyone know if the Front and Rear prop on the VP DPX drive have a required rotational position relative to one another?

I'm reinstalling my props and can match the previously installed position, but I don't know if they had been installed correctly.

Thanks,
Jeff

C_Spray

iTrader: (2)

Clocking position does not matter - Just slam 'em on!

PS - Get your (other) bellows yet?

ThirdBird

No kidding! I would have thought it would make a difference where they are relative to each other. Must be they spin so fast opposite each other that it makes no difference?

Magicfloat

Interesting. On Merc Bravo 3's it is very important that they are positioned perfectly.i.e..the blades on the rear prop must cover the spaces between the blades on the front prop.Off even a little and you lose performance and get cavitation.Strange that it doesn't matter on Volvos.

Westcoast

I never heard that one...are you sure?

Magicfloat

Absolutely. There is even a service bulletin from Merc from years ago with a drawing of how they are positioned.A few years ago we had a customer complaining about reduced performance.Turns out he removed his props to paint the drive,just stuck them back on without alignement,lost a few mph. Ask any Merc dealer,it is fact.

Westcoast

good to know...thanks

C_Spray

iTrader: (2)

It's a matter of what position they are in when the path of water off of the front blade intersects the leading edge of the rear blade. Maybe it has something to do with the skegs. DPX's have a relatively small and thin skeg.

Nonetheless, it could make for an intersting experiment. Anyone have a copy of the Mercury bulletin?

Knot 4 Me

Yep, this is true. The only Merc reference I've seen showing how to "clock" the props was contained in the engine installation manual that came with my boat. It showed how to clock the old Blackhawk surfacing prop sets. However, the same positioning applies to the Bravo III prop sets.

techman

I used to have a Volvo Duo-Prop on a Cobalt (DPS model) and you had to mount them so that the front and rear prop blades never lined up with the anti-ventilation plate at the same time. VERY IMPORTANT according to Cobalt. I always did it that way but never tried not to.