Issues with my outdrive HELP

I have an issue, when I trailer my outdrive all the way up and I try to bring it down again the hydrulic motor runs but the out drive does not move the only way that I have found this not to happen is if I do not trailer the motor all the way up. The only way that I can get the outdrive to move again if I do bring it all the way up is if I bleed the line a little. Does anyone have any ideas what might be happening. My boat is a 1990 206 captiva Rinker. With an alpha 1 outdrive please help

 

There is no limit switch in the Alpha-1 hydraulics. Tilting all the way cause the pressure to rise sharply at the end: you hear the pump slowing down.
In your case, there is not enough oil, the oil is not the right type (ATF) or the oil is dirty, 3 causes for an air bubble or foam in the pump.
Drain the system completely, fill with fresh oil so that with the drive up there still is some oil in the tank. That should do the trick.

 

To avoid misunderstandings: the correct type of oil is very light machine oil, SAE-5 or SAE-10, like sewing machine oil. Of course there is the proper but over-priced Quicksilver product, but you can buy it wherever hydraulic systems are serviced.