"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.

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

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

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

"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.

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

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

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.

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.

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.