Prop Pitch
Posted: Mon Mar 26, 2012 6:40 pm
I've read all of the posts about props, cavitation, etc. and found something interesting today when I was putting on a new cone zinc
The boat has the original 15X9 sailor prop.
BUT:
From an additional stamping I found on the prop, it seems to have been repitched to 7.5.
I get that the change should theoretically give the prop more thrust (torque?), at the expense of of speed. I'm told the equivalent of about 150 rpms worth.
So my question is why did one of the PO's make this change. Would pitching the prop lower cause any less cavitation in general. If the boat is going slower I assume there ought to be less cavitation, but couldn't that be achieved just by lowering rpms?
I had an occasion last fall motoring into a 25-30 knot wind and chop and the boat barely made headway with crazy amounts of cavitation at around 2500-2700. I actually wound up bearing off and sailing a few tacks close hauled to get back to the slip.
Comments?
Thanks everybody.
BB
The boat has the original 15X9 sailor prop.
BUT:
From an additional stamping I found on the prop, it seems to have been repitched to 7.5.
I get that the change should theoretically give the prop more thrust (torque?), at the expense of of speed. I'm told the equivalent of about 150 rpms worth.
So my question is why did one of the PO's make this change. Would pitching the prop lower cause any less cavitation in general. If the boat is going slower I assume there ought to be less cavitation, but couldn't that be achieved just by lowering rpms?
I had an occasion last fall motoring into a 25-30 knot wind and chop and the boat barely made headway with crazy amounts of cavitation at around 2500-2700. I actually wound up bearing off and sailing a few tacks close hauled to get back to the slip.
Comments?
Thanks everybody.
BB