1980 SeaRay 190

Trim comes up, but only partial down. This makes travel a bit of a
''plow". I looked unsuccessfully to see where I might add fluid to
trim, since I hear the motor hum on both up and down.

Where do I add fluid? What kind of fluid? Had an owners manual, but
have moved a number of times.....and manual gone or in the bottom of
some storage box in the barn.

Roger B