Marine water pumps work just like regular pumps in the sense that the purpose is to supply and pressurize the water from the tank. An alternative name is a boat dock water pump. A pump is chosen based on the number of outlets to be supplied and the flow rate required. If the pump is erroneously rated for the system, the flow will drop off when another outlet is opened.
Operation of a Marine Water Pump
The pump unit has a Hall Effect pressure sensor for the water flow and varies the motor speed to maintain constant pressure. This dispenses with the requirement for an accumulator and pressure switches. The VSD controls the motor speed using a PWM DC motor controller.
Types of Marine Water Pumps
- Diaphragm Pump- These pumps are the well-built and are designed for multi-outlet systems. They are more tolerant to dry running conditions, self-priming, relatively quiet in operation and have inbuilt hydraulic pulsation dampening.
- Impeller Pump- These pumps normally have a pump with bronze casing and nitrile rubber or neoprene impeller. They are less tolerant to running dry and they are self-priming.
Installing a Marine Water Pump
There a couple of installation points to observe when installing water pumps.
- Cable Sizes- Ensure that the cable is rated for maximum current draw and voltage drop. Voltage drop problems are very common, and it is advisable to oversize the cable.
- Connections- Connections directly on to pumps is common. Make sure the crimps are done properly. Also put some vaseline over the connection to stop moisture getting to the connection lugs. Where wire tails require a butt splice, ensure that they are crimped properly. Some pumps with integral pressure switches require connection directly to one side so ensure this has been done properly.
- Bonding- Some metal cased pumps such as wash down pumps must be bonded. This should be taken to the negative polarity of the supply. In the event of a positive short to the case, this trips the circuit breaker.
Consult the experts whenever you’re in doubt about installation of marine water pumps.
Marine water pumps must be tested before you put the boat back in the water. However, you will want to test the outboard in water to ensure everything is working correctly. Rather than using the lake or marine water you can use a tub of water that is deep enough for the outboard. Look for the pee stream and test both gears inside the marine water pump.