I hope someone can help me figure out how to determine the pitch of a
propellor. I am planning to replace my current 2-blade prop with a
folding prop (to minimize drag under sail and to stop catching on
lobster pots thick as a forest in downeast Maine) but need to figure out
the exact prop size to order, based on my current prop (which is matched
perfectly to my 13 HP Westerbeke engine). Since I cannot find out the
reduction ratio on my transmission from the engine manual or any other
markings, I cannot know the shaft RPM at my engine cruising RPM, which
is what the folding prop manufacturer says they want in order to
recommend the right pitch).
My current prop is not marked with pitch--at least I think it's not.
It's got a 13 inch diameter and measures 2 inches deep from the leading
edge of the blade to the trailing edge at its fattest point. The only
markings on it seem to be as follows:
HH94332
H34725
These two are probably the manufacturer's numbers--but no name is shown
anywhere. An internet search turns up nothing for those numbers.
A third number on the prop SEEMS to say 14-14R -- which I MIGHT think
means a 14 inch diameter and a pitch of 14. (And yes, it's
right-handed.) But the prop is clearly only 13 inches diameter, not 14,
so I don't know if I can trust the second 14 as signifying the pitch. I
assume an experienced professional could tell me the pitch by looking at
the shape of the blades (the 2-inch depth), but I don't know anyone here
to ask.
So, anyone have any ideas? Thanks! (By the way, my research and
conversations with several people with folding props (such as the
Martec) confirm they pull very well in forward, gain up to 0.5 knots
under sail with the reduced drag, do not catch lines underwater, and
sacrifice only a little power in reverse. Since I'm on a mooring and not
a dock, I very seldom use reverse anyway).
Tom
Vega 1240
Downeast Maine, USA
propellor. I am planning to replace my current 2-blade prop with a
folding prop (to minimize drag under sail and to stop catching on
lobster pots thick as a forest in downeast Maine) but need to figure out
the exact prop size to order, based on my current prop (which is matched
perfectly to my 13 HP Westerbeke engine). Since I cannot find out the
reduction ratio on my transmission from the engine manual or any other
markings, I cannot know the shaft RPM at my engine cruising RPM, which
is what the folding prop manufacturer says they want in order to
recommend the right pitch).
My current prop is not marked with pitch--at least I think it's not.
It's got a 13 inch diameter and measures 2 inches deep from the leading
edge of the blade to the trailing edge at its fattest point. The only
markings on it seem to be as follows:
HH94332
H34725
These two are probably the manufacturer's numbers--but no name is shown
anywhere. An internet search turns up nothing for those numbers.
A third number on the prop SEEMS to say 14-14R -- which I MIGHT think
means a 14 inch diameter and a pitch of 14. (And yes, it's
right-handed.) But the prop is clearly only 13 inches diameter, not 14,
so I don't know if I can trust the second 14 as signifying the pitch. I
assume an experienced professional could tell me the pitch by looking at
the shape of the blades (the 2-inch depth), but I don't know anyone here
to ask.
So, anyone have any ideas? Thanks! (By the way, my research and
conversations with several people with folding props (such as the
Martec) confirm they pull very well in forward, gain up to 0.5 knots
under sail with the reduced drag, do not catch lines underwater, and
sacrifice only a little power in reverse. Since I'm on a mooring and not
a dock, I very seldom use reverse anyway).
Tom
Vega 1240
Downeast Maine, USA
