Suck or Blow?

[RHough]

Is there a "best practice" for mounting bilge ventilation fans? Should the fan be close to the engine compartment and blow through a long duct to the outlet or should the fan be mounted close to the outlet and suck through a long duct?

[kenJ]

Since all the "bad" fumes the fan is supposed to disperse are low it makes more sense to mount the fan high near the exit and suck through a long tube. Keeps any errant sparks from the fan motor from igniting the fumes you are trying to get rid of.

[RHough]

Originally Posted by kenJ

Since all the "bad" fumes the fan is supposed to disperse are low it makes more sense to mount the fan high near the exit and suck through a long tube. Keeps any errant sparks from the fan motor from igniting the fumes you are trying to get rid of.

Fair enough.

The reason I ask is that most fans are better at blowing than sucking

Thanks for the reply.

[Frosty]

Not only that but if you blow the engine comartment all the smells and fumes will not necceserily go out the hole you want . it will also go through all the little holes and feed pipes spreading fumes throught the boat.

[messabout]

Squirrel cage fans suck pretty good. Centrifugal paddle fans suck even better...Think vacuum cleaners. Conventional bladed fans do not pull air in as well as the other types unless they are tightly shrouded. Think Kort nozzle.

[yokebutt]

Ought to suck about as much as it blows, you know, conservation of mass and all that pesky stuff.

[FAST FRED]

With a std 4 inch engine room blower I'm not sure you could measure the difference, but blowing is more efficent.

However mounting any electrics as far above any possible water is the most rational.

FAST FRED