Bond with Your Bilge Blower

Posted: July 1, 2014

Proper engine-room ventilation cannot be overestimated.

By: Story and photos by Capt. Wilson Sheppard

Bilge ventilation is probably one of the most overlooked engine-room systems, despite its importance in removing dangerous exhaust fumes and fuel vapors from the compartment. Although the bilge blower is built to withstand the harsh engine-room environment, it may pick up dust and debris. You should inspect and clean it every season.

Need to Vent

If your boat has an engine mounted in an enclosed space, the Coast Guard requires that you have a blower to remove fumes and/or vapors that may be lurking in your engine room. It is vitally important that you always run the bilge blower for at least four minutes before starting your engine(s).

While underway, intake vents capture the airflow and redirect it through the engine compartment to remove any fumes and/or vapors. At low speeds, the captured airflow may not be moving fast enough to properly ventilate the engine room, in which case you should run the bilge blower occasionally, but not necessarily for the entire cruise. At the end of your cruise, you should run the blower after shutting down the engine(s).

Ducts in a Row

Gasoline and diesel fuel vapors are heavier than air and will settle to the bottom of the bilge. Flexible ductwork is positioned in the engine room so that one end is near the lowest area of the bilge and the other is attached to the blower. Disconnect the ductwork from the blower and check it for damage, debris and moisture. Replace the entire length of it, if necessary.

Blower Down

Before removing the blower, make sure your batteries are disconnected or off. Also, make sure the blower’s wiring is not bound and is long enough for you to move, inspect and clean the blower. Disconnect the wiring if it will hinder in the removal of the blower.

Remove any mounting screws or bolts while holding the blower. Once it is detached, locate and remove screws along the housing to disassemble the blower (picture 1).

Inside the blower, fan blades are connected to the motor shaft with a retaining nut, a screw or a washer (picture 2). Carefully remove the blades. Wash them with soapy water, wipe them with a soft cloth and rinse them with fresh water.

Next, remove the screws so that the motor is detached from the housing. Lubricate the motor with oil designed for electric motors. Check the motor’s casing for corrosion; if any is present, use a scouring pad or wire brush to remove it (picture 3). To prevent any further corrosion, you can touch up the motor with paint, but be sure it doesn’t get inside the motor or on the spindle.

Before reassembling the blower, wash the housing with soapy water and a soft cloth before rinsing it with fresh water.

Reverse your removal steps to remount the blower and reconnect the ductwork. Be sure to reconnect and secure the wiring.

Replacement Value

If you find any breaks, cracks or other damage to any part of the blower, do not bother trying to service it. Replace it. Be sure you get a blower that is sized to properly ventilate your engine room. Depending on the blower that you select, you may need to replace your ductwork as well.

After reinstalling your existing blower or installing a new one, turn on the blower and make sure it is running without grinding, squealing or stopping intermittently. Place your hand outside the vent to make sure it is moving a good amount of air through the system. Hopefully, you’ll exclaim, “Thar she blows.”


Pop Quiz

How long should you operate the bilge blower before starting an engine? The easy answer is four minutes. Here’s why.

The Code of Federal Regulations (CFR) addresses powered ventilation systems in Title 33 CFR 183.610:

(f) Each boat that is required to have an exhaust blower must have a label that: (3) Has at least the following information: Warning! Gasoline vapors can explode. Before starting engine operate blower for four minutes and check engine compartment bilge for gasoline vapors.

Although this explicitly specifies the information that boat manufacturers must provide to operators, it implicitly sets the amount of time an operator should run the bilge blower. Note: Diesel fuel has a higher flash point than gasoline, but its vapors and engine exhaust fumes are just as dangerous and need to be properly ventilated.

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