I have a 1989 18' Caravelle with a mercruiser engine. I cant lower the prop; a salesman at a local marine shop told me my hydraulic fluid was low. He sold me the fluid and a pistol grip oiler gun and showed me where the reservoir was. I took the allen screw out of the valve to insert the fluid. When i attempted to do so, most of it spilled out. It seems as if it needs to somehow be pressurized in, and a little oiler gun isn't going to cut it. Any suggestions?