"If the pump starts leaking, o
"If the pump starts leaking, or if you have trouble cooling, or if it has not been changed in 5 years or more, you should change it.
If you are talking about the prop shaft stuffing box nut; there should be very little to no leakage. If there is leakage, you need a new seal or stuffing installed. Newer boats use a dry seal stuffing box, which should not leak at all.
You should not run without a T'stat. The T'stat assures that the engine will get warm enough to vaporize most of the water condensation and contaminants from the oil. It also acts as a restriction to the free flow of cold water through the block (with a RWC engine), and reduces cold spots . Running without a T'stat has no advantage.
If you are having trouble cooling with a T'stat installed (that is opening properly), you have a cooling water supply problem, or a blockage somewhere. Running without a T'stat will not fix it.
Rod"