How To

How to Install a Bilge Pump on Your Boat? | Best For Consumer

Installing an automatic bilge pump if your boat is not equipped should be MANDATORY. The bilge pump is dewatering equipment very commonly installed on boats. As its name suggests, it allows you to pump the water that will accumulate in a hold. (the lowest part inside a boat) And so to evacuate it outside through a thru-hull. You read our article on how to clean injectors of an inboard engine.

For the anecdote, the first bilge pump was invented by Archimedes around the year 270 BC. It is a screw pump that was manually operated. Depending on the type of drive, the bilge pumps fall into two broad categories: mechanical/manual bilge pumps and electric bilge pumps.

Electric pumps can be equipped with a water level sensor or a float switch that allows the pump to be operated automatically when there is water in the bilge.

In this case, we speak of automatic bilge pumps. In this article, we will focus on the method of installing an electronic bilge pump.

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Step 1: Prepare the location for installing a bilge pump

Before you begin, it is essential to clean the shims properly in the installation location.

Indeed, one of the main reasons for the failure of the bilge pumps is the presence of solid objects such as grains of sand, debris, or dirt in the pumping circuit.

These solid objects end up damaging the moving parts of the pump.  In particular the turbine, the impeller element or possibly the membrane.

For the location of the pump, locate the lowest point on the inside of the boat where water is likely to accumulate. Then choose a flat surface that is easily accessible to facilitate maintenance and repair operations.

Step 2: Installation of filter and float

The pumping circuit is generally composed of the following elements:

  • A filter.
  • A pump.
  • A trigger float
  • A thru-hull.
  • A pipe.

However, it is widespread to find pumps with the strainer integrated with a single element, which makes installation even more comfortable.

In the rest of the article, when the filter is mentioned, it will be the plastic part integrated into the pump.

Besides, the choice of the pump type will be based on the space available, and it is sometimes easier to install a filter and float at the desired location and remove the pump.

There are also pumps with the filter and integrated float, but their size is more important.

The filter is a metal or plastic part that plays the role of support (base) and filters for the bilge pump.

In principle, it is equipped with a non-return valve to prevent the return of the evacuated water. If this is not the case, it is advisable to install a non-return valve after this one.

To begin, place the filter in the place where the pump is to be mounted. Then use a pen to mark the location of the mounting holes, and then remove the filter.

Using a drill, drill shallow holes in the areas marked with the pen. Fill each gap with a sealing adhesive such as Sikaflex Putty, for example, to prevent water from entering the fiberglass through the vents.

Place the filter on the mounting location and screw it with stainless steel screws. 

Use the same technique for the float taking care to position it as much as possible of the pump filter.

Step 3: Connecting the electrical wires

I have often seen automatic bilge pumps connected to the 12v system after the battery switch. In my opinion, it is necessary to join live on the terminals of the battery; indeed, when you leave the boat, you cut the batteries. If the bilge pump is not connected live, it will never fire, which is silly.

With the pump clipped onto the strainer, run a power cable of a suitable size for the power of the pump – from the ground wire of the pump to the negative terminal of the battery.

Run electrical cables from the “On” position and the “Auto” position of the pump to a 3-way switch located on the cockpit or electrical panel. Then connect the switch to the positive terminal of the battery.

This remains a basic assembly. Otherwise, you must follow the electrical installation diagram supplied with the pump.

Because the electrical cables will be placed in a damp environment, you must use connectors crimped with thermo-retractable sheath lined with adhesive to avoid the risk of short circuits. Preferably, the cables should be routed along a bulkhead or secured with wire ties or plastic cable ties to a pre-existing electrical harness.

About the connection of the trigger float, it should be installed on the “positive” cable and the “automatic” switch.

Step 4: Installing the thru-hull

The thru-hull is the element through which the water will be discharged to the outside.

Its location must be both far enough from the waterline and very close to the pump. Once the place is located, drill a hole in the hull with a diameter slightly larger than the width of the discharge pipe.

Tip: To avoid damaging the boat’s gel coat, drill the hole from outside to inside instead of from inside to out using a suitable drill and a hole saw. Once the work is done, put a little adhesive sealant on the hole and attach the thru-hull after applying Sikaflex generously. For anti-osmosis treatment complete, you may like to read our complete guide for anti-osmosis treatment on a boat.

Step 5: Installation of the discharge pipe

Finally, to install a bilge pump, all you have to do is mount a hose from the bilge pump to the thru-hull.

When mounting, make sure that the pumping circuit is as short as possible and without any significant curvature or bend. Indeed long piping can significantly reduce the performance of the pump and the discharge rate.

Besides, use smooth-walled pipes because the roughness of the inner pipe surface can also reduce the discharge flow.

For fixing the pipe, use stainless steel hose clamps. Finally, check the installation and make sure the pump is working correctly. There you go!

Installation of a bilge pump, what to remember

An automatic bilge pump is one of the most critical safety features onboard a boat. It is ESSENTIAL to have one installed. How many boats sank at the port because they were not equipped with an automatic bilge pump? Too much!

It is wise to have a manual bilge pump besides (fixed or portable). Or a portable electric bilge pump with a built-in battery onboard the boat or the most powerful boat engine.

This allows you to evacuate water from the boat in case of failure of the main pump or case of problems in the boat’s electrical system.

Install a bilge pump: the shopping list: 

  • A filter.
  • A pump.
  • A bilge pump with integrated filter
  • A trigger float
  • A thru-hull.
  • A pipe.
  • from sikaflex
  • The ducts heat-shrinkable
  • Of cable ties
  • A hole saw
  • Of stainless clamps

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