I've got a tilt-trim unit on a 150 Yamaha that has been leaking
fluid for a couple years now. I have had to purge the air out of it
(which is a major pain) if it sits more than a couple weeks or If I
don't keep the fluid topped off.
This season, I've used it several times now without a hitch
or adding any fluid.

......Happy Day!!!
db ~looking forward to a season without screwing with that damned thing.