I presume that by “drainage” you mean bilge pumps, and hull and fire pumps. In pretty much all cases that I have run into, they are electrically driven. In smaller vessels, they are commonly 12 VDC or 24 VDC.
The exception, while not a drainage pump, is the engines own fresh and salt water cooling pumps, which are typically belt driven, the raw water pump, and mechanically driven in the case of the coolant pump. (The salt water cools the fresh water / antifreeze coolant by a heat exchanger, and is discharged overboard with the exhaust, or separately in a dry exhaust installation,)
Larger pleasure vessels that have a constant running diesel generator may use (European) 240 VAC, or (American/Canadian) 120 VAC.
Big ships with big pumps are commonly 3 phase 480 VAC.
Other than engine cooling, the only (usually) direct power driven pumps are the hydraulic pumps for winches, fishing vessel net blocks etc that are on main engine PTO’s (Power Take-Offs.)