Manufacturers recommend you to replace your water pump impeller annually. It is a good idea to have them replaced especially to keep the gear case from getting stuck on your engine from salt water. Keep the drive shaft and shift shaft splines greased and especially the bolt threads. Even though you are seeing water come out of the tell tale, it does not mean it is an efficient amount of water feeding the engine block. The thermostat is a serviceable item that often gets over looked. The thermostat can cause your engine to load up and also make your oil get diluted with fuel when it gets stuck open.