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Old 10-02-2020, 15:33   #1
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Bilge Blower distance

Hello all,

My boat smells like boat and I'm trying to fix that. My first step was to install a Gulper pump on a daily 5 minute timer that keeps my bilge bone dry. That's done.

Then I went to install a bilge blower fan, which I plan to leave on nearly all the time, however, it is way too loud. I have the fan installed in my engine room, which is under the salon floor of my boat. It's just too much noise.

My questions is: I have an aft lazarette with vents out the back of the boat and can run a 3" duct from their thru the bilge to underneath the engine. It is about a 20 foot run though. If I mounted a 150CFM 3" blower back there in the lazarette would it pull that distance? This way the noise would be outside the living area of the boat.

I looked over the specs on the blower and can find nothing about hose length other than to make it as short as possible.

I'm also open to other tips to help get rid of the bilge smell in the boat.

Thanks!!
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Old 10-02-2020, 15:36   #2
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Re: Bilge Blower distance

Pulling enough air through to get rid of the smell will be noisy and a waste of power. I'd try to track down where in the boat the smell is coming from and see if the source is easily fixable. Chances are, it's either permeated hoses on the holding tank or just an area that's grimy / smelly and needs cleaning.
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Old 10-02-2020, 15:44   #3
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Re: Bilge Blower distance

Why not just get a dehumidifier? A dry boat won’t smell once you clean up the mold. Also a bilge pump won’t give you a dry bilge, it will just lower the water level. Only a shop vac and then a sponge will get ALL the water out. Of course if by smell like a boat you mean smell like a toilet, then as stated above you need to fix your toilet system which could mean replacing old hoses, cleaning vents or even going to a freshwater flush. Saltwater is filled with microorganisms which die in the toilet and then stink.
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Old 10-02-2020, 16:45   #4
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Re: Bilge Blower distance

Best and fastest way to dry out your bilge is go for a good long motor (like a good 6 hours at hull speed) The heat and air exchange will dry it fast. Once that’s done grab the disinfectant and scrub brushes and go to town. If it comes back I would start looking at your sanitary hoses as a likely culprit.
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Old 10-02-2020, 17:03   #5
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Re: Bilge Blower distance

I have a large wood boat I liveaboard, and use bilge blowers to power vent the bilge areas. I use a 12v motor speed controllers, bought on eBay for under $5 to reduce the speed to about 20% or less. Just enough to maintain a flow. Bilge areas replace air from dryer cabin air and adding power venting ends the boat smell quickly. My blowers are never off. In a large bilge area, you may need to have multiple exhaust points. I use large plastic pipe with drilled holes placed above the keel. Clothes, bedding and cloth covers will probably have to be washed to get the smell out. Also the type of foam used in mattresses, etc. has an effect of holding smells.

You can also use a rheostat to slow the motor speed. Lots of info on the internet.

Drying the bilge with air eliminates most of the water. Usually in a tight boat the water comes from condensation from breathing, cooking, showers, etc., not leaks. Plus I run a stove all winter and my inside cabin relative humidity runs about 40%. No matter what's happening outside.
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Old 10-02-2020, 20:23   #6
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Re: Bilge Blower distance

Thanks all for the tips.

All the sanitation in the boat is less than 2 years old including hoses and holding tanks. That smell is not it. It's a bilgy grime smell. I'm quite certain that it is the distgusting mixture of water, diesel, oil, etc that was in my bilge until a week ago when I installed the Gulper pump. Before installing that I always had 2 or 3" of water in the bilge that the pumps left. Now, the gulper sits in a little hole in the bilge that goes a few inches down into the keel and gets everything totally dry.

I still have some water that goes in there from rain, A/C condensate, etc, but I've set that Gulper to run automatically for 7 minutes a day. I think the bilge will be dry from here on out.

I've sprayed it out really well but its still not that pretty.

I like the dehumidifier option. I'm wondering if I just leave one on down in the bilge area (it'll fit in my 4 feet deep bilge) if that will eventually kill the smell.

Also, I like the tips from whoever owned the wooden boat. I think some type of constantly running exhaust fan would work well over time.

We use the boat as an Airbnb when we are not actively using it and this is the main reason getting rid of the boat smell is imperative.

AND - we are taking it out on a 5 hour each way cruise this coming weekend so perhaps that engine heat will help eradicate stuff.

THANKS AGAIN!
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Old 10-02-2020, 20:40   #7
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Re: Bilge Blower distance

I've been running a 7" Noctua computer fan for exhaust from the engine space for 6 years - 24x7. I never turn it off. It is incredibly quiet (18db) and draws 1 watt. I built a little holder out of plywood to let it fit on a 4" exhaust hose. You can also get a small one that mates up with the hose but moves a lot less air but might be enough for you.

Besides getting rid of smell, it cools the engine room much faster which is great on hot nights after a long engine run.

https://www.amazon.com/Noctua-NF-A20...1392031&sr=8-1
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Old 10-02-2020, 20:45   #8
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Re: Bilge Blower distance

It’s not just the heat from the engine that does it. Your diesel (assuming) uses a tremendous amount of air and with most diesels drawing combustion air from the bilge and engine compartment you see a huge change over in a short time. I would even go so far as to block your bilge blower I take to ensure it’s drawing from the boat and not outside.

If your bilge water has a smell, usually right after the bilge pump is activated you probably have some oil mixed in with it. The oil sits on the surface and starves the water of oxygen, it percolates creating methane and hydrogen sulfide (smells like swamp gas?) when the bilge activates the oil slicks breaks releasing the gas and smell.
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Old 10-02-2020, 20:48   #9
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Re: Bilge Blower distance

If the smell isn't diesel, it's usually mostly mildew. Mix up the following home made and very cheap mildew spray tested that tested above the commercial ones by Practical Sailor. It's clear, non-staining, no odor, and very safe (all ingredients are used in food products). Spray and wipe down everything, let it dry on the surface to retard future mildew growth. Ingredients are available by the pound on Amazon.

1 quart hot water
2 tablespoons baking soda
2 tablespoons Borax
1 tablespoon TSP
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Old 11-02-2020, 04:43   #10
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Re: Bilge Blower distance

Quote:
Originally Posted by rbk View Post
It’s not just the heat from the engine that does it. Your diesel (assuming) uses a tremendous amount of air and with most diesels drawing combustion air from the bilge and engine compartment you see a huge change over in a short time. I would even go so far as to block your bilge blower I take to ensure it’s drawing from the boat and not outside...
Indeed.
The two primary aspects of a properly designed engine room ventilation system are cooling air, and combustion air.
Cooling Air: The flow of air required to carry away the radiated heat of the engine(s) and other engine room machinery.
Combustion Air: The flow of air required to burn the fuel in the engine(s).
Properly designed engine room ventilation systems will maintain engine room air temperatures within about 8.5 to 12.5°C (15 to 22.5°F) above the ambient air temperature. A 7 to 10°C (15 to 20°F) temperature rise (ΔT) is a reasonable target for engine rooms.
Maximum engine room temperatures should not exceed about 50°C (122°F).
See also Steve D'Antonio’s excellent article “Venting the Engineroom”
https://www.proboat.com/2015/06/venting-the-engineroom/
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Old 11-02-2020, 06:55   #11
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Re: Bilge Blower distance

Good idea to run your engine , generator and all engine room equipment hard. Full on

Then shut down

Then take some measurement to seek out the hot spots

Engine room temp spikes once you turn off the main engine

Chargers , inverters , generators .... generate substantial heat and the first to suffer heat damage

Heat sources like exhaust plumbing need to be well insulated

Hot spots are always up high. Ceiling and dead ends with No air movement

Forced cold air in should always be directed down toward the bilge under the main engine

Never. Direct forced cold air onto the engine ... you will increase temp , blast furnace

Air vent out , forced or natural is difficult to position because of the geometry of a boat

A nice detail is double blowers.. high power blower when machinery on , low power blower. when machinery shut down

A timer switch on the high power blower is a nice idea, automatic shut down after a programmed time
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Old 11-02-2020, 07:46   #12
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Re: Bilge Blower distance

I'll through in my 2 cents into the mix.

The muffin fan blower idea has merit and would be good to keep air flow moving to remove stagnant air under the floor boards/bilge area to reduce smell. The muffin fans are low power draw, move a lot of air and can be low noise.

IMO this is only a band-aid remedy and doesn't help identify and remove the source of the smell. "My boat smells like boat ...." doesn't really nail down the type of smell it is if you are trying to chase it down. Does it smell like diesel, bilge, old boat or head smell? Your nose is a very good detector to find the location. The diesel is fairly easy to identify and will be localized around the engine, fuel line(s) and tank. Fix the leak source and use degreaser (Fantastik) to remove residual fuel.

You've already added the bilge pump and its fairly dry, but are there any other areas that are scummy/still damp. Been in boats the scum accumulation was so bad it smelled like fuel. Check around that there are no pools and also clean under the engine. If some areas under the floor boards are not accessible, try to shoot the mildew spray that CarlF suggested as best as possible.

Did any cabinet wood get soaked from bilge water recently or previously? This can contribute to old boat smell. You'll notice this if you pull out drawers from cabinets and then you get a big whiff of smell. If the wood is dry, would spray again w/mildew solution, let dry, then paint w/a good primer to help seal the wood.

The head smell again is obvious. May need to change hoses, fix a vent, change tank(s), etc.



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Old 11-02-2020, 08:28   #13
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Re: Bilge Blower distance

Your bilge may now be "dry" but, unless you thoroughly cleaned out the residue from the prior oil and diesel fuel contamination, it's still there and off-gassing. (Unfortunately, a little goes a l-o-n-g way!)

A through scrub of all surfaces--including the undersides of the sole--with hot water and something like "Greased Lightening" followed by several flushes with hot water will get rid of most of that. A final treatment that we found effective was to thoroughly wet down the surfaes with lime juice, several times, which seemed to cure the ill entirely. I used to use Lemon Juice for that but an old mechanic suggested Lime Juice was more effective instead and that proved to be the case. One can usually find "bulk" lime juice--gallon jugs--at food whole salers like "Smart'n Final" fairly inexpensively. With that, wahtever venting you decide on will be more effective overall.

FWIW...
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Old 11-02-2020, 10:30   #14
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Re: Bilge Blower distance

To go back to the possible head smell possibility, do you know when your hoses were changed last? If they've been done, then they could be permeated.

When trying to locate the smell stick your nose to the hose or whipe it w/a damp paper towel. If you can smell it, maybe that's the smell you associated w/"boat smell" is the head.
Many threads on CF on the subject, but if no other sources comes up as a stink source would give this a go. We switched to PVC schedule 40 pipe to go to the tank and it did a great job. Depending on the turns in your run you may not be able to do 100% pvc, but minimizing the amount of standard flexible sanitation hose w/help in the long term.
Follow your nose and you will find the source of the odors.


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Old 11-02-2020, 10:35   #15
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Re: Bilge Blower distance

Rent an ozone generator and run it overnight when you are NOT on the boat. The smell will be gone.

Many will tell you that ozone will degrade rubber components and it will but only over a very long period of running (months or years).
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