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post #1 of 9 Old 03-22-2007 Thread Starter
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Bilge Blower - How 2 Install?

Hi, I've heard a lot of discussion about the need for ventilating the bilge when gasoline is involved. I have not, however, heard much about the PROPER way to install a bilge ventilation system. My biggest source of confusion is, where does the output of the blower system come out? Is it desirable to run a duct from the blower to the transom, so that the fumes discharge downwind and not in the cockpit?
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post #2 of 9 Old 03-22-2007
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The outflow is ducted to a dorade at the stern or a vent in the transom.
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post #3 of 9 Old 03-22-2007
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You also have to use ignition-protected switches and fan motors for it... otherwise... it could be a bad thing.

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post #4 of 9 Old 03-22-2007
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Typical the blower (an "explosion proof" or "ignition proof" rated blower) is usually mounted in the engine bay with an intake duct leading down to the bilge spaces, to to the bottom of the engine compartment. That way it is also just a short run for the exhaust. Needless to say the switch for it must be ignition protected as well!

Usually there will be two vents, one facing forward to allow fresh air into the engine spaces, which leads to the top of the engine space. And the second, the exhaust duct, facing rear so vacuum can draw out the exhaust air, which is taken from down low where the fumes may be.

For most sailboats, with an inboard under the cockpit, that "bilge blower" is just ducting the engine compartment--not the actual bilge up midships.
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post #5 of 9 Old 03-22-2007
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Atwood makes a "tubular" one that is generally mounted "inline" in the engine compartment (run dryer-style hose from near the carb out to a transom dorade, but many people still prefer the "squirrel cage" type mounted inside the transom under the coaming, which gets the electrical motor out of the engine compartment entirely. I prefer the latter because I can hear it working via the dorade. You need to run the blower for four minutes by Canadian law, but I fudge this slightly by virtue of hanging the keys on the thru-hull seacock: because I have to open both the seacock, the fuel **** and I give the diaphragm a couple of tugs, I get to have a good look and a good sniff there. If all is clear, I usually fire it up after 90 seconds or so.

I will run the blower on occasion when underway, as motoring or motorsailing with a following wind can put fumes into the cabin. Which is a little too "auto shop" for my taste.

Roger that on the ignition-proofing, regardless, just as you need a non-sparking "marine" alternator for the same reason. A gas sniffer doesn't hurt, either, nor does wiping a dry rag under the fuel bowl occasionally and the annual inspection of the rubber O-rings and clamps.

Gas isn't as dangerous as people make it out to be (you don't see speedboats and cabin cruisers exploding much, do you?), but it wants a fairly strict safety routine and is ultimately less forgiving than diesel.
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post #6 of 9 Old 03-22-2007
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Gas isn't as dangerous as people make it out to be (you don't see speedboats and cabin cruisers exploding much, do you?), but it wants a fairly strict safety routine and is ultimately less forgiving than diesel.
One reason that this is the case, is because of the USCG requirements for the bilge blower in gasoline-fueled inboard engine vessels.

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post #7 of 9 Old 03-14-2012
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USCG Regs for Bilge Blower

Hi all ...

As you might imagine, the Coast Guard has some pretty specific notions as to how ventilating oughta be done.

Click here for their point of view!

MC Passage
Rochester, NY
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post #8 of 9 Old 03-15-2012
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Re: Bilge Blower - How 2 Install?

I wired my blower so it runs whenever the ignition is energized with an override to run when that switch is on. Whatever you do make sure that the blower sucks the air out and not blow fresh air in. The latter arrangement could pressurize the engine compartment and force CO into the other compartments. The arrangements I've seen have the suction hose low in the engine compartment on the same side of the engine compartment as the fuel lines and pump. If you have a bilge elsewhere in your boat that's lower than the engine, don't worry about it just have the suction hose near the engine. I don't use a dorade for the discharge but rather a simple rubber air scoop it is in the stern at deck level with the air scoop faced aft. I'm a coastal cruiser

Walt Elliott
Kingston WA
Puget Sound
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post #9 of 9 Old 03-15-2012
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Re: Bilge Blower - How 2 Install?

Quote:
Originally Posted by Valiente View Post



Gas isn't as dangerous as people make it out to be (you don't see speedboats and cabin cruisers exploding much, do you?), but it wants a fairly strict safety routine and is ultimately less forgiving than diesel.
That's because the USCG has requlations that require the gas powered boats have the ventialtion system. years ago before the regs there were boats burning and exploding on a regular basis.

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