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[email protected] May 21st 04 04:24 PM

Continuos Duty Bilge Blowers
 
I'm tired of replacing my bilge blowers, as these Atwood Continuous
Duty (continuous duty in a pigs eye), inline blowers only last one
season before they start squealing.

I probably use my blowers more than the average Joe, so I need a
blower that offers real, and reliable continuous duty.

I looked at this one, and it does look much more durable than the
little plastic inline blowers, but the motor doesn't look like it
would tolerate a salt environment, though I could be wrong.

http://www.greatoutdoors.com/go/prod...er/amback.com/


Any other recommendations?

Jim Rojas May 21st 04 06:29 PM

Continuos Duty Bilge Blowers
 
That looks like a nice unit. Much better than the cheap Attwood. I have a
similar one in my '76 trihull, that sees nothing but salt water. 32 years
old and it still works fine. Pay attention to the motor housing...that is
what counts. The bracket you have pictured looks galvanized, but it can be
replaced if needed.

Take a look at this link...there are several other models to choose from.

http://www.cnejs-hunting-fishing.com...age_Number=355


Jim Rojas

wrote in message
...
I'm tired of replacing my bilge blowers, as these Atwood Continuous
Duty (continuous duty in a pigs eye), inline blowers only last one
season before they start squealing.

I probably use my blowers more than the average Joe, so I need a
blower that offers real, and reliable continuous duty.

I looked at this one, and it does look much more durable than the
little plastic inline blowers, but the motor doesn't look like it
would tolerate a salt environment, though I could be wrong.

http://www.greatoutdoors.com/go/prod...er/amback.com/


Any other recommendations?




Rod McInnis May 21st 04 07:40 PM

Continuos Duty Bilge Blowers
 

wrote in message
...

I probably use my blowers more than the average Joe, so I need a
blower that offers real, and reliable continuous duty.



There is a basic fundamental problem with any DC motor being considered
"continuous duty": The typical brush type motor will wear out the brushes!

A commutated motor is hard on brushes. The slip ring brushes that are used
on AC motors can last a long, long time, but the arcing and gaps associated
with a commutator cause the brushes to wear. On a motor that is intended to
have a long service life they will put in very long brushes and/or make them
easy to change. The typical "cheap" DC motor, however, when the brushes wear
out you throw the motor away.

If you really wanted to have a long life, continuous duty blower then what
you should do is get a blower assembly, with good bearings that you can
grease from time to time, and couple it to a good motor. Ideally you would
get a "brushless DC" motor so that you wouldn't have these issues.

Unfortunately, the blower really needs to be a "marine" rated item so you
have the additional problem of finding a brushless DC motor that is also
marine rated.

Rod



May 21st 04 11:14 PM

Continuos Duty Bilge Blowers
 
Hey Jim... I hate to tell you but your 31 year old boat is only 28... Well
if it is a '76 as you said!!

"Jim Rojas" wrote in message
...
That looks like a nice unit. Much better than the cheap Attwood. I have a
similar one in my '76 trihull, that sees nothing but salt water. 32 years
old and it still works fine. Pay attention to the motor housing...that is
what counts. The bracket you have pictured looks galvanized, but it can be
replaced if needed.

Take a look at this link...there are several other models to choose from.


http://www.cnejs-hunting-fishing.com...age_Number=355


Jim Rojas

wrote in message
...
I'm tired of replacing my bilge blowers, as these Atwood Continuous
Duty (continuous duty in a pigs eye), inline blowers only last one
season before they start squealing.

I probably use my blowers more than the average Joe, so I need a
blower that offers real, and reliable continuous duty.

I looked at this one, and it does look much more durable than the
little plastic inline blowers, but the motor doesn't look like it
would tolerate a salt environment, though I could be wrong.


http://www.greatoutdoors.com/go/prod...er/amback.com/


Any other recommendations?






Jim Rojas May 21st 04 11:26 PM

Continuos Duty Bilge Blowers
 
Well you get the idea... :)

Jim Rojas

wrote in message
link.net...
Hey Jim... I hate to tell you but your 31 year old boat is only 28... Well
if it is a '76 as you said!!

"Jim Rojas" wrote in message
...
That looks like a nice unit. Much better than the cheap Attwood. I have

a
similar one in my '76 trihull, that sees nothing but salt water. 32

years
old and it still works fine. Pay attention to the motor housing...that

is
what counts. The bracket you have pictured looks galvanized, but it can

be
replaced if needed.

Take a look at this link...there are several other models to choose

from.



http://www.cnejs-hunting-fishing.com...age_Number=355


Jim Rojas

wrote in message
...
I'm tired of replacing my bilge blowers, as these Atwood Continuous
Duty (continuous duty in a pigs eye), inline blowers only last one
season before they start squealing.

I probably use my blowers more than the average Joe, so I need a
blower that offers real, and reliable continuous duty.

I looked at this one, and it does look much more durable than the
little plastic inline blowers, but the motor doesn't look like it
would tolerate a salt environment, though I could be wrong.


http://www.greatoutdoors.com/go/prod...er/amback.com/


Any other recommendations?








Wayne.B May 22nd 04 05:08 AM

Continuos Duty Bilge Blowers
 
On Fri, 21 May 2004 15:24:02 GMT, wrote:
I looked at this one, and it does look much more durable than the
little plastic inline blowers, but the motor doesn't look like it
would tolerate a salt environment, though I could be wrong.

http://www.greatoutdoors.com/go/prod...er/amback.com/


Any other recommendations?


================================================== ========

The ITT/Jabsco blowers are OK. You should get at least 1,000+ hours
out of one with reasonable care and feeding.


K. Smith May 23rd 04 12:44 AM

Continuos Duty Bilge Blowers
 
wrote:
I'm tired of replacing my bilge blowers, as these Atwood Continuous
Duty (continuous duty in a pigs eye), inline blowers only last one
season before they start squealing.

I probably use my blowers more than the average Joe, so I need a
blower that offers real, and reliable continuous duty.


Why?? Fuel or gas leaks?? (hope not)

Once the motor is running at some revs it's sucking in more air than
any blower is likely to move; indeed leaving the blower on at cruise is
robbing the motor of free air supply or at least trying to.

Assuming your engine room is reasonably well sealed, that could be part
of the problem for the blowers??? struggling against the inrushing air
trying to feed the motor??



K


I looked at this one, and it does look much more durable than the
little plastic inline blowers, but the motor doesn't look like it
would tolerate a salt environment, though I could be wrong.

http://www.greatoutdoors.com/go/prod...er/amback.com/


Any other recommendations?



Shen44 May 23rd 04 03:30 AM

Continuos Duty Bilge Blowers
 
Subject: Continuos Duty Bilge Blowers
From: "K. Smith"



Not 100% true. I know of a number of installations that require a constant
blower to assure positive air pressure within the e/r to cover all engine
operating speeds.

Shen
Why?? Fuel or gas leaks?? (hope not)

Once the motor is running at some revs it's sucking in more air than
any blower is likely to move; indeed leaving the blower on at cruise is
robbing the motor of free air supply or at least trying to.

Assuming your engine room is reasonably well sealed, that could be part


of the problem for the blowers??? struggling against the inrushing air
trying to feed the motor??



K




Wayne.B May 23rd 04 03:37 AM

Continuos Duty Bilge Blowers
 
On 23 May 2004 02:30:46 GMT, (Shen44) wrote:

Not 100% true. I know of a number of installations that require a constant
blower to assure positive air pressure within the e/r to cover all engine
operating speeds.


=============================

Also, at low speed, running the exhaust blower can help to keep engine
room temperatures under control on some boats.


Harry Krause May 23rd 04 03:48 AM

Continuos Duty Bilge Blowers
 
Shen44 wrote:

Subject: Continuos Duty Bilge Blowers
From: "K. Smith"




Not 100% true. I know of a number of installations that require a constant
blower to assure positive air pressure within the e/r to cover all engine
operating speeds.

Shen

Why?? Fuel or gas leaks?? (hope not)

Once the motor is running at some revs it's sucking in more air than
any blower is likely to move; indeed leaving the blower on at cruise is
robbing the motor of free air supply or at least trying to.

Assuming your engine room is reasonably well sealed, that could be part



of the problem for the blowers??? struggling against the inrushing air
trying to feed the motor??



K





Ms. Smith's boating advice is, as has been demonstrated here several
dozen times, not very good.

Calif Bill May 23rd 04 05:59 AM

Continuos Duty Bilge Blowers
 

"Harry Krause" wrote in message
...
Shen44 wrote:

Subject: Continuos Duty Bilge Blowers
From: "K. Smith"




Not 100% true. I know of a number of installations that require a

constant
blower to assure positive air pressure within the e/r to cover all

engine
operating speeds.

Shen

Why?? Fuel or gas leaks?? (hope not)

Once the motor is running at some revs it's sucking in more air than
any blower is likely to move; indeed leaving the blower on at cruise is
robbing the motor of free air supply or at least trying to.

Assuming your engine room is reasonably well sealed, that could be part



of the problem for the blowers??? struggling against the inrushing air
trying to feed the motor??



K





Ms. Smith's boating advice is, as has been demonstrated here several
dozen times, not very good.


Neither is your or Shen's. A E/R blower sucks the air out. Not blow air
in. Therefore there should be at the most a slightly negative pressure.



K. Smith May 23rd 04 10:21 AM

Continuos Duty Bilge Blowers
 
Calif Bill wrote:
"Harry Krause" wrote in message
...

Shen44 wrote:


Subject: Continuos Duty Bilge Blowers
From: "K. Smith"



Not 100% true. I know of a number of installations that require a


constant

blower to assure positive air pressure within the e/r to cover all


engine

operating speeds.

Shen


Why?? Fuel or gas leaks?? (hope not)

Once the motor is running at some revs it's sucking in more air than
any blower is likely to move; indeed leaving the blower on at cruise is
robbing the motor of free air supply or at least trying to.

Assuming your engine room is reasonably well sealed, that could be part


of the problem for the blowers??? struggling against the inrushing air
trying to feed the motor??



K




Ms. Smith's boating advice is, as has been demonstrated here several
dozen times, not very good.



Neither is your or Shen's. A E/R blower sucks the air out. Not blow air
in. Therefore there should be at the most a slightly negative pressure.



But that's what I was alluding to Bill, most systems the blower is
designed to be off when the engine is at cruise revs, i.e. it's trying
to expel air from the e/r, whereas the motor wants as unrestricted a
flow "in" that it can get.

Without a specific reason as to why, I would still be asking why does
the blower operate "continuously"???

Anyway save the original questioner gives a reason (say the
manufacturer suggests, but that leads to even more questions)

No matter.

K





LaBomba182 May 23rd 04 01:59 PM

Continuos Duty Bilge Blowers
 
Subject: Continuos Duty Bilge Blowers
From: "Calif Bill"


Neither is your or Shen's. A E/R blower sucks the air out. Not blow air
in. Therefore there should be at the most a slightly negative pressure.


Buzzzzzzzzz!
Sorry, wrong answer.

Maybe on your 18 foot bow rider.
But there are many boats that use blowers to bring air out AND in. And some
(the Lazzaras come to mind) ONLY bring air in to positively pressurize the
engine room. If the inlets are filtered/baffeled correctly it keeps dirt and
salt out of the engine room.

Do a search for Delta T engine room fans.

Capt. Bill

Shen44 May 23rd 04 05:35 PM

Continuos Duty Bilge Blowers
 
Subject: Continuos Duty Bilge Blowers
From: "Calif Bill"

"Harry Krause" wrote


Ms. Smith's boating advice is, as has been demonstrated here several
dozen times, not very good.


Neither is your or Shen's. A E/R blower sucks the air out. Not blow air
in. Therefore there should be at the most a slightly negative pressure.


G Not 100% true.
I'll leave it to the engineers to explain, but, in many installations you'll
find both intake and exhaust blowers.
In one particular application, they upgraded from "naturally aspirated" to twin
turbo's per engine which created that slight negative pressure you mention,
causing loss of peak power and RPM's.
In this case, the natural venting couldn't supply sufficient air and blowers
needed to be added to solve the problem.
BG had a hell of a struggle opening the door to the e/r to begin with.

Shen

Calif Bill May 23rd 04 07:07 PM

Continuos Duty Bilge Blowers
 

"LaBomba182" wrote in message
...
Subject: Continuos Duty Bilge Blowers
From: "Calif Bill"


Neither is your or Shen's. A E/R blower sucks the air out. Not blow air
in. Therefore there should be at the most a slightly negative pressure.


Buzzzzzzzzz!
Sorry, wrong answer.

Maybe on your 18 foot bow rider.
But there are many boats that use blowers to bring air out AND in. And

some
(the Lazzaras come to mind) ONLY bring air in to positively pressurize the
engine room. If the inlets are filtered/baffeled correctly it keeps dirt

and
salt out of the engine room.

Do a search for Delta T engine room fans.

Capt. Bill



We are talking of 14-25' boats here. Big commercial boats, or 50+' yachts:
different story. They also do not have a 3" or 4" attwood fan.



Calif Bill May 23rd 04 07:08 PM

Continuos Duty Bilge Blowers
 
Not on an under 25' boat. Especially one that runs a 3" or 4" e/r fan.

"Shen44" wrote in message
...
Subject: Continuos Duty Bilge Blowers
From: "Calif Bill"

"Harry Krause" wrote


Ms. Smith's boating advice is, as has been demonstrated here several
dozen times, not very good.


Neither is your or Shen's. A E/R blower sucks the air out. Not blow air
in. Therefore there should be at the most a slightly negative pressure.


G Not 100% true.
I'll leave it to the engineers to explain, but, in many installations

you'll
find both intake and exhaust blowers.
In one particular application, they upgraded from "naturally aspirated" to

twin
turbo's per engine which created that slight negative pressure you

mention,
causing loss of peak power and RPM's.
In this case, the natural venting couldn't supply sufficient air and

blowers
needed to be added to solve the problem.
BG had a hell of a struggle opening the door to the e/r to begin with.

Shen




Shen44 May 23rd 04 08:49 PM

Continuos Duty Bilge Blowers
 
Subject: Continuos Duty Bilge Blowers
From: "Calif Bill"
Date: 05/23/2004 11:08 Pacific Standard Time
Message-id: et

Not on an under 25' boat. Especially one that runs a 3" or 4" e/r fan.


This may normally be true, but, if their is a reason for requiring a
"continuous duty" blower on ANY size boat, the "continuous duty" may be for
some reason other than exhausting "flammable" vapors.
Hence the comment, "not 100% true", as there are other possible reasons that a
particular installation may require something other than your norm.....
maintain a positive pressure, exhaust excess heat, etc.

Shen

[email protected] May 24th 04 01:30 PM

Continuos Duty Bilge Blowers
 
On Sun, 23 May 2004 09:44:42 +1000, "K. Smith"
wrote:


Why?? Fuel or gas leaks?? (hope not)


None.........

Once the motor is running at some revs it's sucking in more air than
any blower is likely to move; indeed leaving the blower on at cruise is
robbing the motor of free air supply or at least trying to.


I was under the impression that air was circulated while running, via
an intake/suction effect through the bilge vents. I don't see how the
engines running at high rev's could draw air into the bilge, as
there's no fan or other means of generating suction.

Assuming your engine room is reasonably well sealed, that could be part
of the problem for the blowers??? struggling against the inrushing air
trying to feed the motor??


I don't run the blowers at cruise, as the venturi effect is sufficient
to keep the bilge vented, but it's my "operating procedure," if you
will, to operate them while the generator is running, before start-up
of course, and while idling.

I also have a fume detector in the bilge which is run 100% of the time
I'm on the boat.

May 24th 04 04:23 PM

Continuos Duty Bilge Blowers
 
Actually Bill, you are only half right here.

The E/R blower does move the air out of the engine compartment, but that air
must come from someplace.

Whether the boat has a forced air intake or not isn't the question as the
exhaust blower will cause a forced air intake just from the pressure of it
operating.

Remember, it can't take air out that does not exist, and it can't
continually take air out if there is no supply.

A continuous duty blower, in any engine compartment, works to ensure the
compartment temperatures do not get too high... As we all know, too high of
temperatures used when mixing a combustible fuel with the surrounding air
for engine ingestion can cause the engine to vapor lock and therefore cease
operation until such time as the engine compartment can be cooled for proper
temperature mixing.

"Calif Bill" wrote in message
nk.net...


Neither is your or Shen's. A E/R blower sucks the air out. Not blow air
in. Therefore there should be at the most a slightly negative pressure.





Wayne.B May 24th 04 04:27 PM

Continuos Duty Bilge Blowers
 
On Mon, 24 May 2004 12:30:14 GMT, wrote:

I don't run the blowers at cruise, as the venturi effect is sufficient
to keep the bilge vented, but it's my "operating procedure," if you
will, to operate them while the generator is running, before start-up
of course, and while idling.


==================================

Nothing wrong with that, good practices in my opinion. You just need
to get a heavy duty blower, which as you have found out, does not
apply to the plastic inline models.

Another poster referred to the engines "drawing air out of the engine
room". That does happen to some extent since the engines draw in air
through the intake manifolds to support the cumbustion process.


Jim Rojas May 24th 04 04:50 PM

Continuos Duty Bilge Blowers
 
You can try an 12V automotive radiator fan mounted directly over the exhaust
vent. They last a long time, push alot of air, and are easy to replace.

I seen one boat with multiple computer fans. 4 or more small fans mounted on
a frame. If one fan dies, the rest keep going. Plus the fans cost $5 each at
any electronics surplus store.

Same princple applies to cheaply Air Conditioning a cabin.

The computer fans are mounted on a square frame.
2 reusable home air conditioning filters act as dust catchers for the front
and rear.
A very small water fountain or bilge pump circulates cold sea or fresh water
into a trickle copper tubing array.
The fans simply blow warm air into the array, and out comes nice cool air...

I can provide you a diagram if you like. You can alter the setup to suit
your needs.

Jim Rojas


"Wayne.B" wrote in message
...
On Mon, 24 May 2004 12:30:14 GMT, wrote:

I don't run the blowers at cruise, as the venturi effect is sufficient
to keep the bilge vented, but it's my "operating procedure," if you
will, to operate them while the generator is running, before start-up
of course, and while idling.


==================================

Nothing wrong with that, good practices in my opinion. You just need
to get a heavy duty blower, which as you have found out, does not
apply to the plastic inline models.

Another poster referred to the engines "drawing air out of the engine
room". That does happen to some extent since the engines draw in air
through the intake manifolds to support the cumbustion process.




Calif Bill May 25th 04 07:58 AM

Continuos Duty Bilge Blowers
 

wrote in message
link.net...
Actually Bill, you are only half right here.

The E/R blower does move the air out of the engine compartment, but that

air
must come from someplace.

Whether the boat has a forced air intake or not isn't the question as the
exhaust blower will cause a forced air intake just from the pressure of it
operating.

Remember, it can't take air out that does not exist, and it can't
continually take air out if there is no supply.

A continuous duty blower, in any engine compartment, works to ensure the
compartment temperatures do not get too high... As we all know, too high

of
temperatures used when mixing a combustible fuel with the surrounding air
for engine ingestion can cause the engine to vapor lock and therefore

cease
operation until such time as the engine compartment can be cooled for

proper
temperature mixing.

"Calif Bill" wrote in message
nk.net...


Neither is your or Shen's. A E/R blower sucks the air out. Not blow

air
in. Therefore there should be at the most a slightly negative pressure.





That Sucker fan, does not cause forced air into the bilge, is makes a
negative pressure environment where the air from the intake line, trys to
fill that negative area. If you had a blower in the intake, then there
would be forced air. And the only time I force air in to my engine room is
during the winter, as I install a solar powered Nicro vent over the intake
to keep the humidity down, and dry out the rain water that wants to collect
in the bilge.



K. Smith May 25th 04 11:52 AM

Continuos Duty Bilge Blowers
 
wrote:
On Sun, 23 May 2004 09:44:42 +1000, "K. Smith"
wrote:



Why?? Fuel or gas leaks?? (hope not)



None.........


Once the motor is running at some revs it's sucking in more air than
any blower is likely to move; indeed leaving the blower on at cruise is
robbing the motor of free air supply or at least trying to.



I was under the impression that air was circulated while running, via
an intake/suction effect through the bilge vents. I don't see how the
engines running at high rev's could draw air into the bilge, as
there's no fan or other means of generating suction.


It goes down through the same pipe, once you turn the fan off:-) or
even if you don't (hence the short life), because when the engine is at
some revs, it's scavenging air anywhere it can get it. Lots of
installations rely upon the flow back down that pipe (after the fan is
off) to feed the engine extra air at revs. Any stray fumes in the e/r
will be going into the engine anyway. Don't wash a diesel with degreaser
then start it to dry things out, it'll very unhappily & noisily rev
madly away till it's sucked in the very last of the fumes in the engine
room:-)



Assuming your engine room is reasonably well sealed, that could be part
of the problem for the blowers??? struggling against the inrushing air
trying to feed the motor??



I don't run the blowers at cruise, as the venturi effect is sufficient
to keep the bilge vented, but it's my "operating procedure," if you
will, to operate them while the generator is running, before start-up
of course, and while idling.


Yes that's normal to turn it back on if you slow to sustained low revs
but once at cruise revs & above it's normal to turn the blower off,
unless you have a specific reason.

I also have a fume detector in the bilge which is run 100% of the time
I'm on the boat.


Good idea & they work well, however still not as well as your nose,
which is particularly sensitive to petrol smells.

Thanks for the update & it seems maybe we're agreed; you don't really
need the fan "continuously"? It's to purge the e/r prior to start &
maybe can't hurt if at sustained low revs.

K




[email protected] May 25th 04 04:06 PM

Continuos Duty Bilge Blowers
 
On Tue, 25 May 2004 20:52:13 +1000, "K. Smith"
wrote:

Thanks for the update & it seems maybe we're agreed; you don't really
need the fan "continuously"? It's to purge the e/r prior to start &
maybe can't hurt if at sustained low revs.


I mention "continuous duty" because there are a lot of lengthy idle
speed zones where I operate, so the blowers are used significantly
more than I think the typical in-line blower is designed for. As
such, after a single season of use, one or both is screeching. What
I'm looking for is a higher quality blower that's specifically
designed for continuous duty, as I believe it will last much longer
than the typical Atwood blower.......

Terry Spragg May 26th 04 02:17 AM

Continuos Duty Bilge Blowers
 
wrote:
I'm tired of replacing my bilge blowers, as these Atwood Continuous
Duty (continuous duty in a pigs eye), inline blowers only last one
season before they start squealing.

I probably use my blowers more than the average Joe, so I need a
blower that offers real, and reliable continuous duty.

I looked at this one, and it does look much more durable than the
little plastic inline blowers, but the motor doesn't look like it
would tolerate a salt environment, though I could be wrong.

http://www.greatoutdoors.com/go/prod...er/amback.com/


Any other recommendations?


Use the blower for safety before starting your explosion machine.
After it starts, it will suck air much faster than any vent fan can.
Turn it off. Do not pressurize the engine compartment, especially
if you have a leaky exhaust. Not that you could, you'd need a 50 hp
fan known on the drag strip as a blower or supercharger. Engine air
inducement might be conducted by deck vent. If too tightly sealed,
exhaust could accumulate in the engine compartment. A flame arrestor
metal filter grille on an engine room exhaust vent driven by engine
vacuum seems a good idea, needing only a vent into the engine
combustion intake. A sufficiently strong "Intake air leak" will
evacuate any but the most catastophic exhaust leak into the engine
compartment. Engine air intakes are noisy, and require a dust
filter, so go a little further and build an intake muffler filter
box. Place any such vent as high as possible in the engine
compartment, in case of flooding. Provide a watertigh closure for
submerged running, if you are fitting a schnorkel.

Use the leakage of air into the engine compartment as a cabin heat
circulation function, for instance, by placing the hot water
radiator in the bow. Fresh ventilation air could be drawn through a
heat exchanger incorperated into the engine compartment ventilation
/ combustion air intake filter, to improve efficiency in the heating
system. The heat exchanger might accept cold water for air
conditioning, which could be cooled by a keel radiator pipe. When
it's 130 (F) out, sea water temperature air will be blessedly cool
by comparison, and won't eat up much power.

Some will say you should try to be safer with a tight engine box.
Don't ever depend on a tight engine box alone for protection from
fumes and fire.

Terry K


Rod McInnis May 27th 04 09:18 PM

Continuos Duty Bilge Blowers
 

"Terry Spragg" wrote in message
.cable.rogers.com...

Use the blower for safety before starting your explosion machine.
After it starts, it will suck air much faster than any vent fan can.


A 454 cubic inch engine running at 3000 RPM and wide open throttle would
consume 394 cubic feet of air per minute. That is roughly what a standard
4" bilge blower will move.

Turn it off. Do not pressurize the engine compartment, especially
if you have a leaky exhaust.


Leaky exhausts are bad no matter what. Most bilge blowers draw air out of
the compartment, not force air in.

A flame arrestor
metal filter grille on an engine room exhaust vent driven by engine
vacuum seems a good idea, needing only a vent into the engine
combustion intake.


What?

You use a flame arrester to prevent a flame front in one area (generally a
small enclosed space) from spreading outside to a larger area. Like the
carburetor intake to the engine room. Where are you exhausting this engine
room to that you are trying to protect? Plan on driving this boat through
an explosive atmosphere?

A sufficiently strong "Intake air leak" will
evacuate any but the most catastophic exhaust leak into the engine
compartment.


I have no idea what you are trying to say here. Considering that the volume
of exhaust gases is an order of magnitude greater than the amount of intake
I don't see how you can make such a claim.

Engine air intakes are noisy, and require a dust
filter


Never seen a dust filter on a boat.

, so go a little further and build an intake muffler filter
box.


The air intake noise is nothing compared to the basic machinery noise of
the engine. If noise is a problem, silence the entire engine room!

Place any such vent as high as possible in the engine
compartment, in case of flooding. Provide a watertigh closure for
submerged running, if you are fitting a schnorkel.


Dust filters? Submerged running? Are we talking about boats here, or off
road vehicles? I have equipped vehicles so that they could wade across
rivers and keep running, but it isn't easy. It is not nearly as hard if you
have a diesel. On a gas engine you will have ignition problems long before
you have water ingested by the carburetor. If you are talking about
prolonged operation the starter and alternator will need a lot of attention
as well.


Use the leakage of air into the engine compartment as a cabin heat
circulation function, for instance, by placing the hot water
radiator in the bow. Fresh ventilation air could be drawn through a
heat exchanger incorperated into the engine compartment ventilation
/ combustion air intake filter, to improve efficiency in the heating


If you desire cabin heat, you will be much better off installing a heat
exchanger with a circulation fan and recirculating the cabin air through the
heat exchanger instead of constantly drawing fresh (cold) air into the
cabin.

It is generally unwise to have any air passages between the cabin and the
engine compartment.

The heat exchanger might accept cold water for air
conditioning, which could be cooled by a keel radiator pipe. When
it's 130 (F) out, sea water temperature air will be blessedly cool
by comparison, and won't eat up much power.


I have never been any place that was 130 (F). Where do you boat that gets
that hot? Most of the places that I do freqent where it gets what I
consider to be "hot" the water temperature, at least on the surface, gets to
be 75 to 80 degrees.


Some will say you should try to be safer with a tight engine box.
Don't ever depend on a tight engine box alone for protection from
fumes and fire.


You certainly want to have isolation between the engine compartment and the
cabin, but I have never heard of making the engine compartment itself air
tight. Such a design certainly wouldn't be legal in the USA.

Rod



[email protected] May 28th 04 01:58 PM

Continuos Duty Bilge Blowers
 
On Thu, 27 May 2004 22:57:45 GMT, WaIIy
wrote:

On Thu, 27 May 2004 13:18:53 -0700, "Rod McInnis"
wrote:

A 454 cubic inch engine running at 3000 RPM and wide open throttle would
consume 394 cubic feet of air per minute. That is roughly what a standard
4" bilge blower will move.


You can't have it both ways, there is no "3000 RPM and wide open
throttle".


Depends how the boat is propped! 8) It wouldn't be ideal, but it's
doable.


Rod McInnis May 28th 04 06:42 PM

Continuos Duty Bilge Blowers
 

"WaIIy" wrote in message
...
On Thu, 27 May 2004 13:18:53 -0700, "Rod McInnis"
wrote:



You can't have it both ways, there is no "3000 RPM and wide open
throttle".


Why not?

On my tow vehicle I end up at around 3000 RPM and WOT going up hills fairly
often.

Rod



Rod McInnis June 1st 04 10:23 PM

Continuos Duty Bilge Blowers
 

"WaIIy" wrote in message
...


Get realistic here, we are talking about boats.



Okay, why don't you get realistic?

If you read back on the thread of discussion you may notice that there had
been some discussion about the amount of air the engine was going to draw
into the engine compartment. That is a relatively easy thing to calculate
IF you assume that the engine is operating at a reasonable RPM (no
significant restrictions in the intake) AND it isn't being throttled. An
engine has a certain amount of displacement. If it is a four cycle engine
(and isn't throttled) it will draw that much air every two revolutions.

If the air flow into the engine is restricted then the calculation is much
more difficult. However, if the bit of information you are interested in is
the maximum air flow that you need to be concerned about then assuming WOT
is a reasonable approach. As you throttle the engine the situation will
only get better.

The bottom line is that a typical engine running at typical RPMs will draw
less air than a typical exhaust blower will.

Rod



Rod McInnis June 2nd 04 06:53 PM

Continuos Duty Bilge Blowers
 

"WaIIy" wrote in message
...


Please list the boats that run a 454 at WOT and 3100 rpm.

This is the claim you made that I asked you to address.


You totally missed the point. The discussion wasn't about what RPM an engine
would achieve at Wide Open Throttle, the discussion was about how much air
the engine would draw into the engine room.

If you want to nit-pick and draw things off topic I will counter that I
never made any claim about 3100 RPM. You are the first one to mention that
specific, exact RPM.

If you want to be a bit more reasonable and talk about more general terms as
a means of conveying information then I will point out that on many boats
with planing hulls there will be a period of time that the boat may operate
at WOT while the boat accelerates and climbs up on plane. The RPMs that the
engine achieves during this period will be significantly below the maximum
RPM it will eventually achieve.

To drag this back into the context of the discussion thread: Terry Sprag
said "After it starts, it will suck air much faster than any vent fan can."

I submitted a calculation that shows that a fairly good sized engine,
running at a fairly common RPM would NOT draw air "much faster" even at the
worst operating, which is WOT. Closing the throttle will only strengthen my
position.

If you dispute the argument that I make then offer some reasonable counter
argument, don't just throw needless flak out to confuse the issue.

Rod





Rod McInnis June 3rd 04 09:30 PM

Continuos Duty Bilge Blowers
 

"WaIIy" wrote in message
...


You are showing gross ignorance of what a pleasure
boat engine will do in the real world and "3000 RPM and wide open
throttle" doesn't happen to be part of it.


I am sorry, I have been talking about how much air is drawn into an engine
compartment, not what the operating load on the engine might me. I
appologize if my worst case sceanario confused you.


I give up.


Yet you continue......

Depends how the boat is propped! 8) It wouldn't be ideal, but it's
doable.


If you have a problem with that statement, why don't you go find the person
who said it (it wasn't me) and argue with him?


Please refer to your above quote supporting 3100 (actually 3000 ) and
WOT



What about it?

Since you seem to object to my example that gives an estimate of how much
airflow an engine might draw, why don't you provide one of your own? How
much air do you think an engine draws into the compartment?

Rod




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