The linear drive I finally located (haven't purchased yet) is non-marine.
Rather commercial, industrial for gates, wheel chair lifts and positioning
appliactions.

I is presently available from Surplus Center
http://www.surpluscenter.com/item.as...&item= 5-1474

I'm anticipating that I will have to give some attention to marinizing the
unit, but that's what DIYs do.

Steve
s/v Good Intentions