I've seen an application where Minnkota motors were compensated with air
VIA a scuba tank and regulator. It was simple, clean, and inexpensive.
He said if you see a few bubbles coming out, it's working, if there's
lots of bubbles, the seal is blown, and if you don't see ANY bubbles, water's
gettin' in.
No oil changes either.
A scuba tank can compensate a few motor housings for many hours, and with
a manifold, you can push that air someplace else if you need it.
Submerged air is a valuable resource, much like battery power in that
sense.
I've heard about vegetable oil being used for compensation. Does it have
less resistance? does it produce carbon when burned? Does it decompose into
GOO? Hell! I don't know.
Just seems like air is a better compensating fluid than oil.
Frank D.