Thanks for the reply brotherxb03. Sorry to sound dumb but I really don't know which type. Its a '84 Mariner 200 - if that matters. One main lift cylinder with two other cylinder rods extending only through the trim travel range. Another boating friend told me any lightweight non-detergent oil or non-foaming hyd. fluid would be OK. Still not sure about fluid level though. I have checked by removing filler cap and no fluid is visible - ran cable tie down filler tube and only about 1" of fluid on it.