The march pumps, assuming you're talking about the usual 805/815 pump, produce about 5psi maximum. The hoses don't flail about uncontrollably at that pressure, so they can be used (with caution) with the out end unteathered. I'm also assuming you plan to fill the kettle using the pump, rather than drain it.
When I first built my brewery, I used to simply drop the hose into the BK and pump the mash/sparge out from the MLT. This worked fine, especially since there was a fairly heavy quick disconnect weighing the hose down.
However, you should try to find some way of fixing/clamping the hose to the kettle, or be cautious around the equipment. I forget how I did it, but I ended up getting the hose on the floor and losing some of the first runnings. After that, I installed an inlet valve on the BK just to be on the safe side.
If you plan to drain the kettle, then keep in mind that draining a kettle without a valve with this pump will be tricky, since the pumps are not self priming - they can only push water, so the pump head has to be filled with liquid before it will pump (and running it dry can damage the pump.) If the hose is starting at bottom of the kettle and hung over the wall of the kettle and then connected to the pump, you have to find some way to start a siphon to pull the liquid up out of the kettle and down to the pump - the pump won't do this itself. A valve placed at the base of the kettle will achieve this naturally, using gravity to feed the pump.