Selecting Bilge Pumps for Your Boat

Bilge Pump Capabilities and Functions

Nearly all marine vessels have unwanted water in the bilge, which then must be removed lest it cause serious damage. Water enters the vessel through a propeller shaft packing gland, leaky seams in a wooden boat, leaky portlights, melting ice in the icebox, and many other reasons. Undesirable consequences occur when water is left in large amounts in the bilge. It can destabilize it; distribute spilled fuel throughout the bilge, development of osmotic blisters in fiberglass ship hulls. The boat can even sink. Dubbed ‘nuisance water’, bilge pumps function primarily to remove it. Leaks may be caused by catastrophic Mother Nature in the form of wake taken during a storm or collisions. These dangerous systems call for bilge pumps with high power functioning capacity. Bilge pumps only buy time for leaks to be prepared as the boat ‘limps’ back to shore, or in the worst case to abandon the ship safely and carefully. Having multiple pumps is not only advisable but simply smart thinking. To avoid loss of money, please carefully consider these words of wisdom regarding bilge pumps.

Nowhere does there exist a boat that has a large enough bilge pump system to keep up with a consistent leak cause by hull damage. The pumps themselves are designed and function to keep out small quantities of water from leaks, to prevent water damage to the marine vehicle. The American Boat and Yacht Council (ABYC) stipulates the standards of electric bilge pumps to be as followed, “intended for control of spray, rain water and normal accumulation of water due to seepage or spillage.” In no situation should you leave a leak in a boat alone with a regular, standard bilge pump. This will not keep your boat afloat, as you will come to find out. Get the leak fixed immediately, as the pump will eventually fail to keep the water from your boat and will cause detrimental damage.

Manual or Electric
The easiest and most inexpensive pumps to install are a high-capacity centrifugal pump. They are completely ineffective if the boat electric system fails which will most likely happen when a marine craft takes in a lot of water. Due to this, it is recommended that in addition to electrical pumps, one high-capacity manual diaphragm pump exists in your bilge pump system. These manual pumps are able to move substantial amounts of water, at 20 gallons per minute, but are tiring to implement. One gallon of water weighs over 8lbs, so pumping is challenging for the pump and person pumping. Some of these manual pumps require that the pumper be in an awkward “all fours” position while removing the water. Buckets may be more effective here.

Automatic Operation
Accomplished with either an automatic pump or external float switch, automatic operation, although convenient, is not a good option for keeping a leaky boat afloat. One of the disadvantages of using an automatic pump or external float switch is that you may not be aware that there’s a leak, and it could be progressively worsening and you’d never know. Well, you would after your boat began to malfunction and/or sink. There are some solutions to this issue: having a cycle counter to record the pumps cycles (on and off) as well as log it. Having a buzzer or light that turns on when is in operation is also a good alternative.

What to Search For
Electronic switches: The latest type of switch that uses Mirus™, a type of detector that senses the presence of water through a plastic housing. This senor uses a low-impedance electrical field to detect water with no electronic switches. Without an electronic switch, there is nothing to wear out. It also does not sense petroleum products so it’s safe method of detection that won’t accidentally result in the pumping of fuel overboard if it spills into the bilge.
Integral automatic switches
: Due to the nature of many pumps available on the market, installation is simple. The float switch is pre-wired on one side of the pump. Accomplish this with the Rule Automatic Bilge Pumps that will automatically spin every couple minutes to detect if there’s water. However, the motor will run whether or not the water is present.
Diaphragm pumps:
These kinds of pumps are independent self-priming. They can remove and lift water from the intake hose and expel it outside of the boat’s hull. A membrane is used to decrease and increase volume of the pumping chamber, pushing out and drawing in fluid through a set of unidirectional check valves. Due to their self-reliant nature, they require an external strainer on the end of the intake hose since debris or hair can cause clogging.
Centrifugal pumps
: Non-self-priming and submersible pumps that must be sitting in the water to be pumped. It can remove all water save an inch, working the best where the bilge has a small sump where water is collected. Centrifugal pumps draw fluid into the center of the pump via whirling vanes, and then push it towards an outlet port. A built-in strainer positioned at the base is easy to remove for a quick cleaning. This is vital as the impeller often gets clogged down with debris.

Flow restrictions and getting water overboard: The same volume is moved continually with diaphragm pumps unless otherwise restricted. When plugged up, diaphragm pumps will work harder and harder until it fails and stops completely. Centrifugal pumps respond differently, it will cease pumping gradually until pumping quits altogether. The motor will not fail, but no fluid will be moved. To remove the water a type of siphoning needs to occur. A hose is led from the water to another body of water that is higher than the starting point of the hose. The suction drives the water up backwards. This is why bilge pumps are typically lower than the hull, where the water will empty. Vented loops can be used to avoid back-siphoning.

Intake Maintenance: To prevent debris and buildup in the hose or pump of the intake, it’s recommended to have a strum box or strainer at the end of the intake hose. More often than not, bilge pumps are full of junk so they must be easy to clean. Diaphragm bilge pump valves are built to be able to pass objects as big as marbles, but it’s more difficult for these types of pumps to defend against hair or fiberglass strands.

Determining type of bilge pumps to use:
What type of marine vessel do you own? A large boat like a yacht, operated mainly on calm waters will need a less intense pump system in contrast to a small racing keelboat that sees a lot of rough waters. The following are some suggestions:

Coastal and/or Offshore boats: These kinds of boats require automatic electric bilge pumps in each bilge area that can hold water. They should also have a larger manual pump for backup

Racing sailboats: Required by the standards set by the Special Regulations pertaining to these types of sailboats, these boats must have two manually operated pumps. One must be located in the cockpit and one below cockpit, permanently installed.

Cruising sailboats: Only one large diaphragm bilge pump is necessary, mounted in the cockpit.

Ski boats and runabouts: One submersible electric pump at the lowest point of the bilge or in the stern is all that’s needed for these kinds of boats. Boats that have stern drives may also have the pump under the oil pan of the engine.

Open Outboard Powered Skiffs and Day sailors: A portable piston pump, hand bailer, or bucket is all that’s necessary.

Relationship Between Size and Bilge Pump Type: Rated by their capabilities, electric bilge pumps are measured in gallons per hour (GPH), with no restrictions to the discharge under open flow conditions. The standard rule of thumb is to get the biggest model that is practical for your vessel. Selection of pump is dependent on size constraints and power limitations. Choosing a capacity of at least 1000 GPH or larger is suggested. Pumps that are submersible have a higher functionality/capacity.

Are you replacing an existing pump? Always match previous wire capacity and hose sizes, unless you are replacing the entire pump system from the wiring to the hull. It’s easy with a little extra money to increase capacity slightly and yet keep the diameter of the hose stagnant. Use a larger practical pump size with the new installation.

Components required: The installation of electric bilge pumps requires several items: The pump, a connection to the boat’s batter, on and off switch (most pumps use manual or float switches). Float switches will automatically activate a pump after the water has risen high enough. An intake hose (can be corrugated, especially if the bilge is lower than the pump) if installing a diaphragm pump (from the pump to the lowest spot in the bilge). A smooth discharge hose from the pump through the hull for overboard water discharge. Lastly, a thru-hull fitting is needed above the waterline for a proper siphoning.

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