Bilge blower for intake air??

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andythilo

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My engine has trouble running under hot conditions, I.e if it's been running a while or n warmer weather. It occured to me that a lack of cool fresh air could be an important factor?

I'm thinking of fitting a bilge blower to act in reverse to supply fresh cool air from the outside blowing aroungld the air intake, worth trying?

Thanks

Andy
 
I assume there is an air inlet to your engine compartment? If so, why not run the bilge blower in its normal mode ie to suck warm air out, to be replaced by fresh air via the air inlet.
 
Air intake

I would suggest that it would be more efficient to have a fan taking hot air out. This is the arrangement on our Jeanneau and it works well.
ray
 
My understanding is that a bilge blower is there to exhaust bilges /engine bay of vapour and or gas before a petrol engine is started up thus avoiding the possibility of an explosion.

A diesel engine should suck plenty of air on its own account.

Of course, my understanding could just be wrong.

73s de

Johnth
 
JohnTH said:
My understanding is that a bilge blower is there to exhaust bilges /engine bay of vapour and or gas before a petrol engine is started up thus avoiding the possibility of an explosion.

A diesel engine should suck plenty of air on its own account.

Of course, my understanding could just be wrong.

73s de

Johnth
Click to expand...

You are correct John,

I suspect the original poster needs a proper inlet of fresh air piped form outside to the lower part of the engine compartment.

This arrangement will cause any hot air to rise and be extracted by the engine air intake.

just make sure the intake has some form of protection to prevent water entry.

We run twin VP's in fully enclosed sections of the hulls, both are fed by 6 inch spiral pipe to the floor of the engine compartments, engines run cool at all times, even on one 47 hour non stop run to put some didtance between ub a cyclone bearing down.

Hope this helps.

PS: we have no blowers.

.
 
oldsaltoz said:
You are correct John,

I suspect the original poster needs a proper inlet of fresh air piped form outside to the lower part of the engine compartment.

This arrangement will cause any hot air to rise and be extracted by the engine air intake.

just make sure the intake has some form of protection to prevent water entry.

We run twin VP's in fully enclosed sections of the hulls, both are fed by 6 inch spiral pipe to the floor of the engine compartments, engines run cool at all times, even on one 47 hour non stop run to put some didtance between ub a cyclone bearing down.

Hope this helps.

PS: we have no blowers.

.
Click to expand...

So how are your pipes run? You say you have no blowers? How is the cool air brought into the engine compartment?

I was thinking that I would simply have a blower blowing near the air filter so provide clean cool air at all times. At the moment my engine cover is raised in the cockpit with vent holes in the sides. I would like to seal it all up to prevent unwanted smells and reduce noise, so inlet blower and bilge blowers would be required. I would probably hook up the inlet blower to the ignition switch.

Good/Bad idea?
 
andythilo said:
So how are your pipes run? You say you have no blowers? How is the cool air brought into the engine compartment?

I was thinking that I would simply have a blower blowing near the air filter so provide clean cool air at all times. At the moment my engine cover is raised in the cockpit with vent holes in the sides. I would like to seal it all up to prevent unwanted smells and reduce noise, so inlet blower and bilge blowers would be required. I would probably hook up the inlet blower to the ignition switch.

Good/Bad idea?
Click to expand...
In my Bene 381 and in my other 351 there was a sucker (squirrel cage fan) which came on with the ignition. this has a pipe to the top of the engine compartment which sucks the hot air out and it exits over the sugar scoop, there is also 2 other inlets on the top of the scoop which one of is led to the bottom of the engine compt and the other is hust to ventilate the scoop insides. The blower sucks all the hot air out and cool air comes in to the bottom of the engine compt.
Normal on most frog boats I have looked at.
Stu
 
Beneteau 323

Has a cold air inlet ( No Fan ) and an extractor ( Fan ) . Great place to warm your hands . Problem is the confined space and sound insulation . You need the extract pipe as high as possible .
 
Yeah ok makes sense. I'll have to think about my installation as the engine cover is a raised section about 8" high and 1' x 2' in dimension.
 
andythilo said:
So how are your pipes run? You say you have no blowers? How is the cool air brought into the engine compartment?

I was thinking that I would simply have a blower blowing near the air filter so provide clean cool air at all times. At the moment my engine cover is raised in the cockpit with vent holes in the sides. I would like to seal it all up to prevent unwanted smells and reduce noise, so inlet blower and bilge blowers would be required. I would probably hook up the inlet blower to the ignition switch.

Good/Bad idea?
Click to expand...

Hi Andy,

Lets start with the basics, think about just one of the engine cylinders and the volume of air it draws in when the intake valve is open, even on a small capacity diesel this would be around 2 cups of air, so at just 2,000 revs per minute they single cylinder gulps (2000/4=500x 2 cups = 1000 cups of air per minute) that's 16.67 cups per second multiplied by the number of cylinders you have.

So based on the above there is no requirement to add a blower to feed the engine box with a blower, the engine draws enough air to keep plenty of fresh air circulating in inside.

Many air intakes of fresh air are via the vents on the cover located in the saloon, but this can be noisy and smelly.

By closing off the cabin (or in your case cockpit vents) and replacing the air supply with a flexible tube supplied from the deck level via a dorade vent to prevent water entry will reduce noise and smells.

The flexible pipe should be cut so that air enters the bottom of the engine compartment, this ensures and water is directed into the bilge, the cool air entering the bottom of the compartment also helps push any hot air up to the intake and reduce the ambient air temp in the compartment.

If you get any engine smells 'after' you shut down, you might like to consider a small blower that sucks air from the compartment and blows it to an external outlet.

Hope this helps.
 
Yes makes sense, thanks. I have a bilge blower already fitted, although whoever installed it fitted it so the pipe is basically on the bilge floor.

I will move the bilge blower hose to the top of the engine and install an inlet hose on the other side of the engine compartment at the bottom.
 
andythilo said:
Yes makes sense, thanks. I have a bilge blower already fitted, although whoever installed it fitted it so the pipe is basically on the bilge floor.

I will move the bilge blower hose to the top of the engine and install an inlet hose on the other side of the engine compartment at the bottom.
Click to expand...

.
Don't bother, in it's present location it should remove any gas or other heavier than air smells, it;s normal for blowers to be installed down low. it will remove any warm air because the piped inlet will drew clean iar in when the blower is running and the engine is stopped.

Avagoodweekend......:)
 
oldsaltoz said:
.
Don't bother, in it's present location it should remove any gas or other heavier than air smells, it;s normal for blowers to be installed down low. it will remove any warm air because the piped inlet will drew clean iar in when the blower is running and the engine is stopped.

Avagoodweekend......:)
Click to expand...
Ahh but all the major frogs do it the other way around!
Stu
Ohh!! sorry, forgot, you,re upside down there!!
 
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