Next time you see an O/B jet look at the foot and you'll see a hose making a
loop on the side, you disconnect that to grease you bearings than
reinstall. The O/B impellers are aluminum, usually stock, and gravel peens
the sharp impeller edges over and cuts down on it's efficiency, you can
take them off and sharpen them again, but the S/S impellers last longer,
but do vibrate a little more I think due to the weight increase. One thing
I've noticed is that my O/B doesn't cavitate near as much as my buds I/B.
The split clamshell that is on most I/B's is much more efficient when
backing up and during slow speed maneuvering because of the three impellers
and their in line flow characteristics.