2 bilge blowers, 1 intakes and 1 exhausts?

collawash

Seaman
Joined
Oct 2, 2004
Messages
51
My '99 Chaparral Sig 27 came with 2 cheap inline blowers that I decided to replace cause I couldn't stand the buzzing noise when I trolled. I replaced them with some Jabsco blowers that are super quiet and very efficient. 1 blower brings in air and the other exhausts. I was always told that all bilge blowers should be exhausting with ports for intake. I have other hoses from the vents to the bottom of the bilge that are not connected to a blower too. <br /><br />Is there a USCG reg or boatnut common sense that has a definitive answer?
 

prockvoan

Chief Petty Officer
Joined
Jul 27, 2004
Messages
512
Re: 2 bilge blowers, 1 intakes and 1 exhausts?

Your blowers should both be exhausting air out.Those extra air ducts vent the bilge when under way.Your vents should have one facing to the bow of the boat,and the other one should be facing the stern of the boat.In fact,you should have at least 3 if not more hoses,one for the power blower and 2 for natural venting when under way.Now this is on each side of the boat.Those hoses that are not hook up to anything go all the way down to the bottom of your bilge.That is were all if any gas vapors will be building up.Make sure that they are set in place,not just hanging there.Email me,I will give you a phone number to call if you need more info.
 

Elk Chaser

Petty Officer 2nd Class
Joined
Jul 29, 2003
Messages
186
Re: 2 bilge blowers, 1 intakes and 1 exhausts?

Based upon the regulations prock is correct for the most part. <br /><br />
<br />Ventilation <br />All boats that use gasoline for electrical generation, mechanical power, or propulsion are required to be equipped with a ventilation system.<br /><br />A natural ventilation system is required for each compartment in a boat that:<br /><br /><br />1. contains a permanently installed gasoline engine;<br />2. has openings between it and a compartment that requires ventilation;<br />3. contains a permanently installed fuel tank and an electrical component that is not ignition-protected;<br />4. contains a fuel tank that vents into that compartment (including a portable tank); and<br />5. contains a nonmetallic fuel tank.<br /><br />A natural ventilation system consists of a supply opening or duct from the atmosphere (located on the exterior surface of the boat) or from a ventilated compartment or from a compartment that is open to the atmosphere, and an exhaust opening into another ventilated compartment or an exhaust duct to the atmosphere.<br /><br />Each exhaust opening or exhaust duct must originate in the lower one-third of the compartment. Each supply opening or supply duct and each exhaust opening or duct in a compartment must be above the normal accumulation of bilge water.<br /><br />A powered ventilation system is required for each compartment in a boat that has a permanently installed gasoline engine with a cranking motor for remote starting.<br /><br />A powered ventilation system consists of one or more exhaust blowers. Each intake duct for an exhaust blower must be in the lower one-third of the compartment and above the normal accumulation of bilge water. <br /><br />For boats built prior to 1980, there was no requirement for a powered ventilation system; however, some boats were equipped with a blower.<br /><br />The Coast Guard Ventilation Standard, a manufacturer requirement, applies to all boats built on or after August 1, 1980. Some builders began manufacturing boats in compliance with the Ventilation Standard as early as August 1978. If your boat was built on or after August 1, 1978, it might have been equipped with either (1) a natural ventilation system or, (2) both a natural ventilation system and a powered ventilation system. If your boat bears a label with the words "This boat complies with U.S. Coast Guard safety standards," etc., it is probable that the design of your boat's ventilation system meets applicable regulations. Manufacturers of boats built after 1980 with remote starters are required to display a label that contains the following information:<br /><br />WARNING<br />Gasoline vapors can explode. Before starting engine, operate blower at least 4 minutes and check engine compartment bilge for gasoline vapors. All owners of boats equipped with exhaust blowers are strongly encouraged to take the same precautions before starting a gasoline engine. All owners are responsible for keeping their boats' ventilation systems in operating condition. This means making sure that openings are free of obstructions, ducts are not blocked or torn, blowers operate properly, and worn components are replaced with equivalent marine type equipment.<br />
So each blower needs to be an exhaust blower and you must have one additional duct installed for each blower for intake air with the opening 2/3 of the way down into the engine compartment at a minimum but above the normal bilge water line. <br /><br />If your boat has a powered exhaust system then I believe it does not need an additional natural ventilation system as the existing system acts as a natural ventilation system when the blowers are off and you are underway.
 

collawash

Seaman
Joined
Oct 2, 2004
Messages
51
Re: 2 bilge blowers, 1 intakes and 1 exhausts?

I need to buy more duct to bring it to code and change the flow on the one blower. I guess you can never have too much ventilation with 100 gallons of gas under your feet. Thanks.
 

18rabbit

Captain
Joined
Nov 14, 2003
Messages
3,202
Re: 2 bilge blowers, 1 intakes and 1 exhausts?

We got our first diesel engine about 1 ½ years ago. There is no going back to gasoline. Diesel fumes do not ignite like gas fumes. Given the efficiency, convenience, and safety on a boat, I can’t see anything but a diesel on a cruiser.
 

collawash

Seaman
Joined
Oct 2, 2004
Messages
51
Re: 2 bilge blowers, 1 intakes and 1 exhausts?

Hey 18rabbit, in several years when my 7.4 is tired and Mercruiser puts out a high out diesel that will fit my engine comaprtment, I will join the diesel club. gas sucks in a boat.
 
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