On the Meyers E-47 pump, the pump relief valve is set at 1650 psi. That means if the resistance of the load exceeds that amount, the lift cylider will stop getting fluid, because it will flow through the relief valve instead. This is to prevent pump damage.
I have moved 2 plows at the same time before with mine, and it lifted the 2 blades together with ease. I got tired of hand trucking them around the yard, and figured out a way to bolt the lift chains together. I'd pull up with mine, and drop it onto the other, right behind the moldboard, onto the A frame. Then bolt the lift chains together. Lift both, and drive the 30' to the back of the yard with them. I wouldn't drive down the road like this, but it was easier than hand trucking the blades across the grass.
~Chuck