Who manufactured it? Some of those cast "bronze" propellers coming out
of China have a large content of iron, which they do to save money. I
have even heard that they will pass off a cast iron, copper plated
part as a bronze casting, although I don't think that is the case
I don't think it was "flawed in some way" it looks like what we used
to call on the railroad a "detail fracture" where something happened
to the surface, and then later a crack "grew" from it.
I read a welding book once where a brand new, big-ass tractor axle
broke because a welder accidentally touched the live electrode to
the axle. A crack that looks just like yours, developed accross the
5"-6"? axle and it snapped right in two. And generally speaking
almost nothing in this world could break that axle like that
It was already mentioned, and I want to ask about the rusty looking
spot/flake that appears in the starting point of the crack. Need to
figure out what that is to be sure... a closer-up picture of it?
It could easily be the reason for the crack... could have started
with a rock ding or something iron you ran over and thought nothing
of it at the time.
"whew... thought that was going to break the prop or something...
glad it didn't.. hardly scratch it"
Just collected some more bits of information regarding my broken propeller
that I'd share with you:
Seems like the propeller is NOT made from aluminium bronze which I thought
it was! The material should be Manganese Bronze (which supposedly is the
same as Hi tensile brass?)
This material should be well suited for propeller use - BUT not for high
powered crafts. My engine has 300 hp and a torque of 700 Nm - which is over
the limit of what a (die cast?) manganese bronze propeller is suited for.
(all this according to one of the leading Danish marine propeller-experts)
Also, the company that imports the Italian "Radice" (manganese bronze)
propellers have had problems with them operating in arctic waters near
Greenland. Seems as the cold water increases the risk of cracks.
Interesting, because my boat has been in the water all winter at
temperatures of down to -1 degree centigrade.
All in all it seems as if the boat-company wanted to save the extra 30% that
a NAB-propeller costs and installed this type instead. Pity what some people
will do to save a buck....
Again thanks for your valuable information - which I think played a part in
the fact that the insurance-company decided to pay for the damage. AND -
install a NiBrAl-propeller instead!