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Installation Instructions for cowl vents, dorade boxes and guards.

Cowl vents, dorade boxes and dorade guards
Cowl vents sitting on teak dorade boxes with dorade guards

The first step is to decide which deck location(s) will be suitable to mount the dorade, mushroom ventilator, and dorade guard if one is being installed at this time.  You need to consider the traffic patterns commonly used to move about the boat.  Can you go around the ventilators or do they become an obstacle nuisance.  Before you start drilling into the deck consider for a moment what is below.  Is there any electrical or plumbing that needs to be avoided.   Can the opening in the deck be clear of all bulkheads.  Will the airflow that enters into the space below provide adequate ventilation. Can you mount a trim ring to the headliner?  Do you have good access to the knob of the Low Profile Ventilator to adjust the amount of airflow into the cabin space.  You must determine the thickness of the deck to decide whether you can thru bolt the fittings of the ventilator or do you need to mount it using sheet metal or wood screws. 

Stainless low profile mushroom vent
Stainless low profile mushroom vent

You have chosen the site to drill the opening in the deck.  Is the deck flat or does it possess some amount of camber to deal with.  If it is flat then you can proceed to the first step.  Here you will decide if you want to reduce the height of the dorade box keeping in mind that if you choose to use a Low Profile Ventilator you will need to consider the maximum height of the open ventilator to clear the bottom of the dorade.  Once you drill the opening it is suggested that you seal the core of the deck with either epoxy or polyester resin.  You can proceed to mount the Low Profile Ventilator.  It is quite light and can be mounted with screws.  You should first add a bedding compound like butyl Tape or 4200 caulking compound before securing the ventilator for waterproof protection.

Fiberglass round dorade box
Fiberglass round dorade box

If your deck has a camber to it you will need to decide if you want to leave the bottom of the dorade flat or to cut the bottom of the dorade to compensate for the camber.  This can be easily done with a protractor and marking the angle of the deck unto the surface of the dorade.  There are a number of tools that can be used to cut the dorade ranging from a bandsaw to a hack saw.  If you are comfortable and proficient you can also use an electric skill saw.  Be sure to use face and eye protection which ever method you choose.  Apply epoxy or polyester resin to the raw fiberglass edge.

Fiberglass round dorade box
Interior of the fiberglass dorade box

Step number two involves mounting the Dorade box.  Before you begin, it is important to make one or more weep holes in the sides of the dorade where the seawater can escape through the weep holes where the dorade sits on the deck.  You have been provided with (2) Heavy Duty  stainless steel angle brackets to secure the Dorade to the deck.  Fasten the brackets to the inside wall where the Dorade edge meets the deck.  Calculate the center of the dorade over the Low Profile Ventilator.  Continue now to mount the brackets to the deck.  I would advise thru bolting the fasteners because of the added weight of the Cowl Vent and the unlikely possibility of wrapping lines around the vent.  They also become valuable hand holds when moving about the boat particularly when the sea and things get dicey.

Low profile cowl vent and fiberglass round dorade box
Low profile cowl vent and fiberglass round dorade box

Step number three involves mounting the Deck Plate to the top of the Dorade.  If a hole has not been drilled into the top, now is the time to measure for the center of the dorade so that a hole saw can drill the appropriate size hole.  For a 3" Deck Plate a 3-1/2" hole saw will be used and for a 4" Deck Plate a 4-1/2" hole saw is used.  Because you are drilling into polyester fiberglass it is imperative to use a hole saw with a strong blade.  Otherwise you will quickly destroy the unprotected blade.  Before mounting the Deck Plate, use a small amount of butyl tape or 4200 to the surface of the dorade.  Also seal the exposed fiberglass surface of the dorade with epoxy or polyester resin.  Mount the Deck Plate to the Dorade with screws, lock washers and nuts that have been provided.

dorade guard base or foot
Stainless standard foot for dorade guard

Step number four describes mounting a Dorade Guard to the deck.  The Dorade Guard offers many benefits to the safety of the crew and protection of the Cowl Vent and Dorade from lines, sails, emergency rafts, wayward dinghies  other gear often hand tied to the Dorade Guard.  It has been designed to be mounted in several possible positions in relation to the Cowl Vent.  It can be mounted looking forward or turned 180 degrees to face aft.  Sometimes it is positioned to face starboard or to turned to face the port side.  Which ever position is used most importantly it must be strongly secured to the deck with a minimum of 3/16" fasteners thru bolted with a backing plate.  Once again epoxy the holes in the deck and bed the guard feet to the deck with butyl tape or 4200.  Keep in mine that the dorade guard has been fabricated with 1" tubular Type 304 stainless steel with a wall thickness of 0.060".  It has one welded joint connecting the three legs.  It is strong but does have its limitations.  It will provide many years of service if you treat it accordingly.

dorade guard
Stainless dorade guard

This is a brief description of the installation of the Ventilation Package consisting of the Cowl Vent, Deck Plate, Dorade, Low Profile Vent, and Dorade Guard.  I am certain that there may be additions and comments which I encourage.  Thank you for your business and smooth sailing.

If you have any questions or would like to place an order please call me at +1 (415) 895-8395 or visit

Dorade guard with fiberglass box and teardrop cowl vent
Custom dorade guard with fiberglass box and teardrop

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