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.
1. Maintain Battery Health
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.
2. Using the right tools for the job
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.
3.Making the right connections
To continue you will need the following items
- Multi-meter
- Heat-shrink butt-connectors (including step-down butt-connector)
- Crimp tool
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.
Final thoughts
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