"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

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 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.

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.

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.

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

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.......