Bilge blowers...

There really are two schools of thought on blowers and positive or negative pressure in the ER. If you have a very well sealed ER then a little positive pressure can be a good thing. It means the engines are getting more than enough air and the engine room will stay closer to ambient air temp.

If your ER is not well sealed from the rest of the boat then a bit of negative pressure can be beneficial to keep odors and soot out of the living areas. But to much negative pressure and you can suck the A/C out of the living areas and perhaps even salty air in and the boat may not cool well underway.

For example, the Lazarra's had well sealed ERs and were designed so the blower ran at positive pressure. At the end of a days run the ER was about as cool as you'd find barring ones with A/C in them. On the Broward's the ERs are not well sealed, so I like to run them at slightly negative pressure.
 
quote:
Originally posted by CurrentSea

Ok, so if they suck, then running a blower at cruising speed may do very little as the air rushing in may negate the air being sucked out!! Make any sense?

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At high speeds or if you do not have large enough vent and/or blowers, yes. And you do not want the engine fighting for air.
 
On a diesel the only time I run the blowers is after a run to help cool the ER.

Usually blowers suck air out, although on the boat I run we have a set blowing air in in the forward area and another set pulling air out in the back of the ER.
 
On the smaller Johnson's do they have those very over sized Delta T fans that take up way to much space like on their larger boats? In the larger boats between the fans and their plenums it can make it difficult to service the gensets. The fans are really over kill.
 
to the OP, in diesel engine room the blowers serve a different function than gas. during engine operation at speed the blower(s) are working against the engine intake. probably not an issue but not really needed as diesel engines are like big vacuum cleaners at speed. in a gas engine the blower(s) are removing fumes from the bottom of the engine compartment rather than just extracting heat.

as others have noted squirrel cage type on a rubber hose or similar soft mount will remove almost all of the blower noise compared to a hard mount.
 
I have no experience with diesels but probably a good idea to run blowers before starting gas engines, when idling, or operating at low speeds.
In a perfect world, or bilge, there are no dangerous fumes. But in the event that something is wrong down there that you don't know about the blowers should remove the fumes before you have a real problem.
I don't really see a down side to using them in a gas boat, and although I have no diesel experience, I don't understand a down side to using them there either.
 
One thing to consider running a boat with the blowers on,(in or out) is that in a fire situation you may be adding oxygen to make things worse.
I have installed a lot of attic fans. They come wired with a firestat which will disconnect the power to the fan at around 180 degrees. here is a 120v model
http://www.northerntool.com/shop/tools/product_200459662_200459662?cm_mmc=Google-pla-_-Fans-_-Fan%20Accessories-_-17267&ci_src="17588969&ci_sku=17267&ci_src=17588969&ci_sku=17267&gclid=CMr13oWqkMACFeRj7Aod_VEAZg.
 
Billy ,
Add a smoke detector ... to kill power ... FIRE in basement ... Attic fan will make a chimney

Rob
 
quote:
Originally posted by BillyK

I don't know if it is made for 12v, but if it's not it should be.

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Yes they make systems that will kill the blowers in the advent of a fire. But you really need to be able close off the vent openings as well to choke off the oxygen to the fire.
 
in a fire, you would want to turn off the bilge blowers so as not to dilute the Halon or other fire suppression system.

diesel engine rooms commonly tie an ignition kill function to the fire suppression system because of the amount of fresh air the engine(s)ingest.
 
quote:
Originally posted by Capt. Bill1

On the smaller Johnson's do they have those very over sized Delta T fans that take up way to much space like on their larger boats? In the larger boats between the fans and their plenums it can make it difficult to service the gensets. The fans are really over kill.

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On the 70 the blowers are outboard of the engines on the ceiling and are not in the way of anything...

They really help cooling the ER after a run, without them it s impossible to spend more than a few minutes down there when the engines are hot. With the blowers on, you can survive long enough to get something done :)
 
Ditto Pascal

In my experience "bilge blowers" are intended to suck heavier fuel vapors out of the bilge, and they're plumbed to the lower parts of the engine room. They won't do much for hot air at the top of the engine room.

Blowers (the bigger the better) taking their suction from the top of the engine room DO make a difference in cooling the ER, especially right after you shut down a hot engine or two.
 
quote:
Originally posted by PascalG

quote:
Originally posted by Capt. Bill1

On the smaller Johnson's do they have those very over sized Delta T fans that take up way to much space like on their larger boats? In the larger boats between the fans and their plenums it can make it difficult to service the gensets. The fans are really over kill.

Click to expand...


On the 70 the blowers are outboard of the engines on the ceiling and are not in the way of anything...

They really help cooling the ER after a run, without them it s impossible to spend more than a few minutes down there when the engines are hot. With the blowers on, you can survive long enough to get something done :)

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To bad they didn't learn from that. In the 87's and 103's while they pull out all the heat they are way over sized and really crowd the gensets. And there are 4 of them. 2 in an 2 out. They could have just use 1 of each and still moved plenty of air.

Then again, if you're the size of the average Chinese boat yard worker maybe it's not such an issue. :-)
 
I have an exhaust fan in my head. Noisy as hell. (you already know where this is going) Usually just open the ceiling hatch, or use it to mask those sometimes. . . .ahem, natural sounds. At some point I had to tip the electrical panel down for some work. There it was. The bathroom exhaust fan-blower. It is a engine compartment blower ducted with the same plumbing hose to an overboard exhaust vent.
 
Yesterday at HD I saw these and thought about this thread. They are 120v and in a galvanized housing, but a reasonable quick fix to see if you get the results you were looking for.

IMG_20140904_151409_zps3c2d7878.jpg
[/URL]

Billy K.
 
quote:
Originally posted by BillyK

Yesterday at HD I saw these and thought about this thread. They are 120v and in a galvanized housing, but a reasonable quick fix to see if you get the results you were looking for.

IMG_20140904_151409_zps3c2d7878.jpg
[/URL]
Don't use these on a gasses unless they're ignition protected. We all know this but sometimes newbies read this too.
Billy K.

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