Bilge Blowers

[A Lee]

I have 4 Bilge blowers that are on separate breakers. With D12 engines, what is the recommended procedure for blowers? I have been told run them always, run them when at idle for extended period, run them after shut down to dissipate heat etc. Would like to hear advice/input.

[Viper]

Are you talking about the 3-4" exhaust blowers that should be turned on for 4-5 minutes prior to starting the engines, or the large flat circulation fans? Aside from turning on the exhaust blowers prior to starting, some folks keep them running for as long as the engines are. I don't see a down side except to say that it'll likely shorten the life of the blower unless its duty cycle is designed for that. If it's the large circulaion fans you're talking about, they're usually installed in diesel applications to maximize air flow to the engines, are typically controlled automatically when you turn the engines on, and are designed to run for hours (continuous duty). Some systems will also keep the fans running for a while after the engines are shut down.

[A Lee]

I am referring to exhaust blowers. With gasoline engines, I understand the importance of running prior to start up. With diesels, I am getting feedback that is all over the place in terms of usage. I understand that some boat designs do not allow enough free air flow for the turbos. If that is not the case( which is not on 56 Voyger ) I assume the blowers are to reduce engine room temperature?

[Viper]

Yes any hot air you displace through either exhausting or circulation will be replaced with cooler outside air. The cooler denser air will maximize air/oxygen flow to the engines. While diesel applications aren't as explosive as gasoline, it's still desirable to be able to exhaust air from the bilge.

[bud37]

An interesting consideration is how much fresh air a running engine brings in....at about 700 cu inches you would be pulling about 200 CFM at 1000 rpm per side......fun with numbers...

[rjr]

It's the argument about diesels requiring vast amounts of air. Why remove air from the engine room? More air should be introduced into the engine room.

[Viper]

Source of the post It's the argument about diesels requiring vast amounts of air. Why remove air from the engine room? More air should be introduced into the engine room.

Technically you're not removing air, you're displacing it. You can't remove air from the compartment without it being replaced with air from outside otherwise you'd have a vacuum. Displacing the inside air with cooler outside air is what you want for the engines. You can do that by blowing in or exhausting out.

[denpooch]

My boat (gas) is designed to have the exhaust blowers running automatically whenever the engines are turned on.