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How to Install a Bilge Blower

by Chris Stevenson

The bilge area in the engine compartment can be one of the most dangerous locations on a marine vessel. If not properly ventilated, the bilge can build up harmful combustion vapors and spontaneously ignite, causing a explosion. Fume buildup in the bilge also contains carbon monoxide that adversely affects humans, causing nausea, disorientation and sometimes unconsciousness and death. Any boat owner should install a properly functioning bilge blower in their engine compartment, even if their vessel has only a large box cover.

Step 1

Open your bilge blower kit and note the two mounting holes in the flange of the motor. Look for a suitable location to mount the blower on the back of the transom or to the underside portion of the deck. Consider the length of flexible duct you will need to attach to the outflow end of the blower to the exhaust vent or collector box, and then the length of the inflow side of the blower where the hose enters the bilge area.

Step 2

Use a drill motor and a small bit to drill the two mounting holes in the blower bracket into the transom or deck. Make sure the flow arrow on the bilge blower housing faces the exhaust side. Use a screwdriver to secure two galvanized screws in the mounting bracket.

Step 3

Use wire cutters to cut the flexible duct to length for the top duct. Use the wire cutters to cut the bottom length of duct needed. Make sure the bottom hose does not enter the sump area of the bilge, but lies above the stringers.

Step 4

Use tie straps to secure the upper duct to the exhaust vent or collector box neck. Pull the tie straps tight. Secure the bottom hose to the bilge blower motor neck with a tie strap. To secure the end of the bottom hose that enters the bilge area, loop a tie strap around it and tighten it. Drill a hole through the excess tie strap end and screw it into a stringer with a screwdriver using galvanized screws.

Step 5

Run a length of 16-gauge wire from the negative terminal of the battery to a suitable location on your dashboard for the on-off switch. Use wire strippers to cut the wire to length. Use wire strippers to cut another wire to length that reaches from the positive battery terminal to the switch location. Mount the switch on the dashboard and use a drill bit to scribe mounting marks through the switch bracket holes.

Step 6

Use a drill and bit to drill the mounting holes for the switch bracket. Twist each end of the two wires (four ends) and place an eyelet on each end. Crimp the eyelet connectors with wire strippers. Connect the negative eyelet wire to the negative terminal on the battery by attaching it to the battery cable nut. Tighten the nut with a socket. Route the negative wire to the switch and connect the eyelet to the negative terminal on the switch. Tighten the eyelet nut with a socket.

Step 7

Connect one positive wire eyelet to the positive battery cable nut. Tighten the nut with a socket. Connect the other end of the positive wire (eyelet) to the positive terminal on the switch. Tighten the terminal nut with a socket. Snip the positive wire in half about 1 foot away from the positive battery terminal. Place a crimp connector on both ends of the wire and crimp them secure with wire strippers.

Place an in-line fuse between the two wire crimps and push the fuse wires into the crimp sockets. Crimp the ends with wire strippers. Place the negative cable back on the battery and tighten it with a socket. Turn the bilge blower switch to the "On" position to test the motor operation.


  • To get the proper diameter of the duct to fit the exhaust vent or control box neck, split the duct lengthwise for about 3 inches and fold the duct in on itself to lessen the diameter. Secure it with a tie strap.
  • If you have only a large battery box, use a hole saw to cut a larger hole that will accommodate the blower duct. Use a vent that has a neck diameter the same as the duct and secure it with tie straps. Screw the vent down on the side of the engine box.

Items you will need

  • Bilge blower
  • Socket set
  • Ratchet wrench
  • Drill motor and bits
  • Screwdriver
  • Wire cutters
  • Wire strippers
  • Flexible blower duct (3- or 4-inch)
  • Stainless steel screws
  • Fuse holder
  • Marine-rated on-off switch
  • Wire (16-gauge)
  • Wire eyelets
  • Crimp connectors

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