The problem is the possibility of a failure that will let the
raw water pump on your engine suck air through the
salt water pump. But then, all my
salt water needs come in one seacock, which can be closed from the
cabin above, and I consider that a
safety feature.
So, I'm going to take a middle path on this question. Yes, you can do it, but use reinforced hose, good connectors, double hose clamps, and a good pressure pump. Turn the
salt water on and off with a faucet, not by stopping the pump. Then, there is not a
route for air into the engine's system.
That's all easier if you use a small
electric pump, which will keep you from getting lazy and failing to close the faucet - it will keep right on pumping until you do. They do not use any of your limited energy
budget when not in use, and not much during your brief needs for
salt water.
Good luck with it.