One of the most important devices on your boat is the bilge pump. A properly wired bilge pump can give you confidence when out at sea as well as when you leave the boat after a weekend of use. A poorly wired bilge pump can also spell disaster. In this article I will go over the necessities to wiring a standard bilge pump and float switch (actual models pictured above) as well as provide guidelines to mitigate the risks of causing irreversible damage to your boat and maintain the overall integrity of your vessel. To skip to wiring instructions scroll down to step 3.
One of the most common service calls I get is "Something's wrong with my boat... "The engine starts but the rest of the items on my boat aren't working.." "There must be some sort of loose wire or something". I've heard this exact phrase countless times. Here's why - most first time boat owners aren't told about the necessity to maintain batteries. And they are not told about the different functions each battery on the boat serves.
Most boats have what is called a "House" battery or batteries. This battery is separate from the engine start batteries and is responsible for operating all of the pumps, lights, electronics, etc. on the boat. This battery is typically isolated from the rest of the batteries unless the engine is running and actively sharing it's charge along with the other start batteries. It is VITAL that this battery or batteries stays charged all the time, even when you are not using the boat. Below is an example of a high quality charger that I personally recommend for smaller boats with one house battery.
The reason why it is important to invest in a portable charger or use the onboard charger (if you have one) is because this battery is responsible for powering your bilge pumps when you are not around. Many cases there is nothing wrong with the bilge pump on a persons boat but a dead house battery caused it to fail to bail the water out of the boat. In some unfortunate cases a boat can "sink" on land or on a lift when the batteries die and water continues to collect in the engine compartment with nowhere to go. Engines and other electrical components found in the engine compartment can get submerged under water causing expensive repairs and often lead to continued issues down the road.
There is an inside joke within the marine service industry whenever someone comes across wire nuts in a boat. "Oh it's one of these guys.." as they roll their eyes and prepare themselves for what may lie ahead. Having a false confidence when it comes to any kind of wiring to your boat can easily create vulnerabilities in your electrical system and put your boat at needless risk. If ever you have any questions regarding your electrical system on your boat I highly recommend asking a certified ABYC technician in Marine Electrical (such as the good folks at SN Yacht Services) to get any dependable information and guidance.
When it comes to bilge pumps you will need proper heat-shrink wire terminals as well as the proper crimping tool. Heat-shrink "butt connectors" used to connect various items throughout the boat come in 3 common sizes: Large 10-12 gauge (Yellow), Medium 14-16 gauge (Blue), and Small 18-22 gauge (Red). In this installation example we will also be using a "step-down" butt-connector that ensures proper joining of the two wires from your bilge pump and float switch.
Many times I'll find heat shrink terminals (sometimes even from factories) that have been compromised by using the improper crimp tool. Below is an image of a proper crimp tool to be used with heat shrink as it will not pierce the waterproof shell when crimping the wires in place.
You can also use standard butt-connectors but will have to slide an additional piece of heat shrink over it to keep it suitable for the bilge environment (pictured below).
To continue you will need the following items
- Multi-meter
- Heat-shrink butt-connectors (including step-down butt-connector)
- Crimp tool
The first step in installing a bilge pump is to correctly identify the wiring coming from your boat. First, turn off any manual bilge pump switches that may be on at the helm before you proceed to test any wires. A typical bilge wire setup-up includes an "always hot" wire, "switched hot" wire, and a negative wire. Identify these 3 wires coming from the boat and get them into position by cutting any zip ties or removing any obstacles in the way.
Start by placing your negative test lead on a DC negative battery post or common DC negative bus bar. It is important that you are confident you are placing the negative test lead to a proper ground source in the boat; not all black wires are DC negative and not every piece of bare metal is grounded to the DC negative system.
With your multi-meter set to DC (symbol with solid line with dashes underneath), use the positive lead to test each wire, one at a time, for voltage. You should only be checking the 3 incoming wires from the boat and not any wires coming from a float switch or other devices in the bilge. Only one wire should show voltage at this time - this will be your "always hot wire". Label this wire and carefully set aside so as to not make contact with the other wires.
Now turn on the manual override switch at the helm. Use your multi-meter to identify which of the other two wires this is. You should see this voltage coincide with the operation of the switch on the dash. Once you are confident you have the correct wire, label and carefully set aside.
Through process of elimination the other wire should be your ground. Confirm this by placing the negative test lead to this wire and the positive lead to the "always hot" wire to verify you are getting proper voltage. Make sure you are confident of your labeling and the polarity of the wires before moving forward.
Now, connect the DC negative from the boat directly to the black wire on the new pump and crimp the connection. Next, take the "always hot" wire and connect it directly to any one of the two gray wires coming from your new float switch.
This next part is important to get correct: insert the remaining gray wire from the float switch and the remaining brown wire on the bilge pump into the yellow end of the step-down butt-connector and crimp. Now insert the remaining "switched hot" wire from the boat into the other end of the butt connector and crimp.
Now test the function of the float switch by inverting the float. The bilge pump should turn on and off automatically via the float switch. Now test the manual switch at the helm and the bilge pump should coincide with the switch.
After you have verified proper operation of the float and switch you can now apply heat to the heat-shrink and continue to mount the pump and float switch accordingly.
If you are a do-it-yourself boater I hope this article has helped you in some way or given you a broader understanding on your boat's electrical system. Many service calls can be prevented with vigilant maintenance and proper installation of parts. It is our mission to simply help boaters navigate their way in boat ownership and lend a helping hand whenever needed.
Happy boating
As an expert in boat maintenance and electrical systems, I want to share with you some valuable information about the importance of properly wiring a bilge pump on your boat. With my extensive knowledge and firsthand experience, I will provide you with all the necessary concepts related to this topic.
The bilge pump is one of the most crucial devices on your boat. When wired correctly, it gives you confidence while out at sea and when you leave the boat after a weekend of use. However, a poorly wired bilge pump can lead to disaster. In this article, I will guide you through the essentials of wiring a standard bilge pump and float switch, while also providing guidelines to mitigate risks and maintain the overall integrity of your vessel.
One common issue that boat owners encounter is when their engine starts, but the rest of the items on the boat aren't working. This is often due to a lack of knowledge about maintaining batteries. Most boats have a separate battery, known as the "House" battery, which is responsible for operating pumps, lights, electronics, and more. It is vital to keep this battery charged at all times, even when you are not using the boat.
Investing in a portable charger or using an onboard charger is crucial because the house battery powers your bilge pumps when you are not around. Many cases of bilge pump failure are caused by a dead house battery, leading to water accumulation in the engine compartment. This can result in expensive repairs and long-term issues.
When it comes to wiring bilge pumps, it is essential to use proper heat-shrink wire terminals and the appropriate crimping tool. Heat-shrink "butt connectors" in three common sizes (large, medium, and small) are used to connect various items throughout the boat. In this installation example, we will also use a "step-down" butt connector to ensure the proper joining of the wires from the bilge pump and float switch.
Using the correct crimp tool is crucial to avoid compromising the heat shrink terminals. Standard butt connectors can also be used, but an additional piece of heat shrink must be slid over them to make them suitable for the bilge environment.
To install a bilge pump, the first step is to identify the wiring coming from your boat. Turn off any manual bilge pump switches at the helm before testing the wires. The typical bilge wire setup includes an "always hot" wire, a "switched hot" wire, and a negative wire. Use a multi-meter set to DC to test each wire for voltage, one at a time. The wire showing voltage will be your "always hot wire." Turn on the manual override switch at the helm to identify the other two wires.
Once you have identified the wires, connect the DC negative from the boat to the black wire on the new pump and crimp the connection. Connect the "always hot" wire to one of the gray wires from the new float switch. Insert the remaining gray wire from the float switch and the remaining brown wire from the bilge pump into the yellow end of the step-down butt connector and crimp. Finally, insert the remaining "switched hot" wire from the boat into the other end of the butt connector and crimp.
After completing the wiring, test the function of the float switch by inverting the float. The bilge pump should turn on and off automatically. Test the manual switch at the helm to ensure proper coordination with the bilge pump.
Once you have verified the proper operation of the float switch and manual switch, apply heat to the heat-shrink and proceed to mount the pump and float switch accordingly.
If you are a do-it-yourself boater, I hope this article has provided you with helpful information about your boat's electrical system. By practicing vigilant maintenance and proper installation of parts, many service calls can be prevented. Our goal is to assist boaters in navigating their way through boat ownership and offer a helping hand whenever needed.
Happy boating!
