Attwood Clamshell Vent, 2-3/16 Inch Opening, Large, Part 66400-3

The attwood 66400-3 is a Large size clamshell vent with a 2-3/16 inch opening, designed for hull-mounted ventilation on boats. It installs as a complete unit by fastening from either inside or outside the hull, making it flexible for a range of mounting situations. A ventilation hose (sold separately, not included) twists into the bottom of the box, forming a raised water barrier that helps keep moisture out of the ventilated space while still allowing airflow.

Built from corrosion-resistant plastic, this vent will not discolor over time, holding up well in the marine environment. It is designed for either intake or exhaust ventilation and meets ABYC H-2 cross sectional area requirements, so it can be used to help ventilate bilges, engine compartments, or other enclosed spaces that need code-compliant airflow. The clamshell shape sheds water effectively while the box-and-hose design keeps the vent opening clear of debris.

Specifications

• Brand: attwood
• Manufacturer Part Number: 66400-3
• Category: Ventilation
• Size: Large
• Dimensions: 0.75 inches H x 4 inches W x 5.75 inches L
• Weight: 0.0908 pounds
• Material: Plastic
• Mounting: Hull-mounted, fastens as a complete unit from either inside or outside the hull
• Hose Connection: Ventilation hose twists into the bottom of the box (hose not included)
• Certification: Meets ABYC H-2 cross sectional area requirements
• UPC: 022697664006

Frequently Asked Questions

What size opening does the attwood 66400-3 clamshell vent have? The attwood 66400-3 has a 2-3/16 inch opening and is classified as a Large size clamshell vent.

Does the 66400-3 vent come with a hose? No, the ventilation hose is not included with the attwood 66400-3 clamshell vent; the hose twists into the bottom of the box separately.

Can this vent be mounted from outside the hull only? No, the attwood 66400-3 is designed to install as a complete unit by fastening from either inside or outside the hull, giving flexibility depending on the installation location.

Is the attwood clamshell vent suitable for both intake and exhaust ventilation? Yes, the 66400-3 clamshell vent is designed for either intake or exhaust use and meets ABYC H-2 cross sectional area requirements.

What material is the attwood 66400-3 vent made from? It is made from plastic that is corrosion-resistant and will not discolor over time, suited to the marine environment.

How much does the attwood 66400-3 vent weigh? This clamshell vent weighs 0.0908 pounds.

What are the dimensions of the attwood clamshell vent? The attwood 66400-3 measures 0.75 inches high by 4 inches wide by 5.75 inches long.

Does the clamshell design help keep water out? Yes, the hose connection on the 66400-3 forms a raised water barrier at the bottom of the box when the ventilation hose is twisted into place, helping block water while allowing air to pass.

Will the attwood 66400-3 vent discolor in sunlight or saltwater exposure? No, the plastic construction is corrosion-resistant and designed not to discolor.

Is the attwood 66400-3 vent compliant with marine ventilation standards? Yes, it meets ABYC H-2 cross sectional area requirements for marine ventilation.

What is the part number for this attwood clamshell vent? The part number is 66400-3, a Large size clamshell vent with a 2-3/16 inch opening.