My motor wouldn't lift the keel after launch last year. Luckily, a fellow boater noticed/ heard me struggling with the boat back out of the water and came over. Turned out he is involved with heavy machinery for a living, and he realised the pressure release valve was lifting too early, before the hydraulics had enough pressure to lift the keel. Half a turn in on the adjuster and bingo, problem cured. He said this is quite common with older hydraulics - the spring in the valve looses tension with time and the preload needs increasing. The valve has a locknut on it and an allen key fits in the adjuster, on the hydraulic motor itself.