Grease Pump In Stern Gland - Is Using It Like This Ok?

[charliehows]

I've noticed that if i give the grease pump into the stern gland a few pumps when ive finished with the engine for a few days, i dont get water in the shaft bilge. Ive always been a bit hazy about how to use the pump, sometimes i give it a few pumps if the engine has been running continuously for a few hours. Anyone able to explain to me exactly what its designed to be used for and whether im gonna do any harm using it the way i have been?