Either you're confused or I am. Old fogeys like me were brought up to
never use stainless below the waterline. Although this rule has been
relaxed somewhat, broadly speaking, stainless is less satisfactory
than bronze -- its advantage lies only in lower cost.

Prop, strut, shaft, and rudder on inboard power boats under sixty feet
or so(which I'm guessing is what we're talking about here) always used
to be made of bronze. This gave good strength, excellent corrosion
resistance, and long life. Bronze has, however, gotten more and more
expensive and stainless has gotten relatively cheaper, so that now it
is cheaper to use stainless than bronze. Bronze is still the more
satisfactory material as it is much more corrosion resistant and is
somewhat stronger, allowing for smaller shaft sizes. (I'm painting
with a broad brush here, as there are many different bronze alloys,
but almost all of them do better than 303/304 or 316 stainless.)

The only time you might be happier with a stainless prop rather than
bronze is after hitting something hard, as the stainless prop might be
less chewed up. Even there, however, it could be debated, as it is
easier and cheaper to rebuild a badly damaged bronze prop than a
stainless one.

As for no-nos, stainless is OK (not great) if you use all stainless.
It's also OK if you use a bronze prop on a stainless shaft -- many
sailboats do this now -- provided you put a shaft zinc on. You're
less likely to want to do this on a powerboat shaft that will spinning
much faster, but electro-chemically it's fine.


Jim Woodward
www.mvFintry.com


(kim) wrote in message . com...
Can someone tell me the advantages/ disadvantages of stainless steel
running gear (prop, strut, shaft, and rudder). I remembered hearing
that it was a no-no, but I have nothing to prove either way.

A boat I test drove had this installed, and it does'nt make sense why
someone would dump all this money into the running gear if it provides
no additional structural, corrosion resistance, or performance
enhancements.

Thanks!