[C320-list] Air duct to engine

[Jeff Hare]

Hello,

These hoses are essentially worthless.  You'll have FAR better airflow to
the engine if you simply remove them and perhaps put a piece of screen over
the inside of the intakes that are mounted on the transom.  These little
hoses are too small for the run length, kinked, rippled inside, make tight
bends, have zip ties squeezing them and probably have junk sitting on them
further reducing the airflow.  When they're connected to the vents, that
means very little air gets in or out of those vents without finding a way
through the hose.

So, the one that connects to the "fan" is the Bilge Blower.  This blower is
installed at the factory because, who knows, there might be someone left who
thinks a diesel needs a bilge blower to keep the diesel fumes from exploding
while starting your engine. Makes sense with gasoline engines though.

So, here are a few different suggestions.

1.  Ditch the hoses completely and use bug screen over the openings.  This
will allow the engine to suck in as much as needed, easier and with less
restriction.  It will also allow the heat from your refrigerator compressor
to exit through those vents and will be more efficient and keep that aft
locker cooler.  With the bilge blower connected, that vent is highly
restrictive unless the blower is running.

2.  If you're one of those who think the bilge blower is useful for cooling
down the aft cabin.   I did an experiment using my little graphing
thermometer in the aft cabin after motoring for several hours 3 years ago.
Try it yourself.  The aft cabin didn't cool down one bit faster with the
bilge blower running for 30 min than it did without the bilge blower running
at all.  And my ears felt better.  But if you still want them, replace the
dryer hose with 4" smooth wall hose used for dust collection and now, you'll
get more airflow, but not as much as if you simply remove the hoses. You can
quiet your bilge blower a ton by mounting it on a thick layer of neoprene to
isolate it from the mounting brackets.

3) If you simply must have these hoses, leave the hose to the bilge blower
next to the fridge connected, but cut the hose so that it ends right in
front of your fridge radiator and use the bilge blower to vent the heat your
fridge compressor generates.

USCG doesn't require bilge blowers in diesel powered boats any more.

My opinions of course.
-Jeff 



-----Original Message-----
From: C320-list [mailto:c320-list-bounces at lists.catalina320.com] On Behalf
Of Graeme Clark
Sent: Monday, July 27, 2015 4:02 PM
To: c320-list at lists.catalina320.com
Subject: [C320-list] Air duct to engine

On the transom there are two air vents, one is the exhaust vent of the
extractor duct from the engine compartment running through the electrical
fan*

The other is - on my yacht - a long white plastic duct which terminates in
the aft locker space, under the rudder cables just lying on the floor!
I suspect this is not where it should terminate!

I have a nasty suspicion that the previous owner may have tampered with it
whilst installing the ducting for a cabin heater but I'd sure like to know
where it's supposed to go and what it does, as everything seems to work fine
at the moment!
Thanks
Graeme Clark
#366, Jaskar

(*By the way, the fan will only switch on if the ignition is switched on.
This means if the engine isn't running I get the low oil pressure sounding
which if I run it for any length of time, annoys neighbours! Any reason I
can't rewire  it to a different live source?)