RE: [omc-boats] Additional Engine Cowl Cover Forced Air Ventilation

Gee…..a picture of this would be so great……I know I know…no photos
allowed on the list - sigh.
 
-----Original Message-----
From: owner-omc-boats@... [mailto:owner-omc-boats@...]
On Behalf Of lib1@...
Sent: Sunday, September 24, 2006 6:34 PM
To: omc-boats@...
Subject: [omc-boats] Additional Engine Cowl Cover Forced Air Ventilation
 
Awhile back there was a post that mentioned a sterndrive boat seemed to
run better with the engine cover removed.
 
The discussion got into maintaining proper ventilation of enclosed
engine bilge areas, a critical marine safety factor.
 
Last winter I installed a Gas Detector monitor from CruzPro. See:
HYPERLINK
"http://www.adventurercomputer.com/new_page_8.htm"http://www.adventurerc
omputer.com/new_page_8.htm for details.
 
 
It works really well. So well, in fact that if I do any extended
trolling or idling it will usually trip on & off. This isn't really a
false alarm, it's caused by the fumes the engine gives off when idling,
I think in the form of crankcase blow-by. I can crack open and prop-up
the clamshell lid and enough extra fresh air gets in to stop the alarm.
But that's a pain. My bilge blower takes longer to clear the alarms,
mainly because iit's designed to pull the heavy fuel vapor fumes off the
bottom, under the engine.
 
Another, factor is I have the 65-66 style Reveler/Sportsman 150-155
clamshell, one piece, engine cowl with the Buick-inspited, six portholes
or "ventiports" as Buick originally called them. When I stuffed the
bigger small block Chevy V8 into the same space as the smaller V6 Buick
things got a little tighter.
 
So I had 4 extra 4.75-inch, 12-vdc computer muffin fins lying about. I
removed the 1/4 plywood flat pieces that are inside the engine cover
directly behind the portholes on each side.
I then took a new plywood piece, and I cut two 4-inch holes on each
piece. After mounting the fans to pull outside air into the engine
compartment, I sealed the unit using some strips of foam. By sealing the
"chamber" it forces the fans to only draw in fresh outside.
 
It's very quiet, even with all four fans running. The idea is to
introduce a steady stream of fresh air into the engine bay, even when
the boat is not moving forward. The vents are high enough that I believe
the engine's flame arrester/carb will get plenty of fresh air. I haven't
finished the wiring yet, but I will provide a fused power source and
control switching. I want to be able to operate these fans independently
from the bilge blower. Each van draws about .75 amp, so all 4 running is
about 3 amps, which isn't very much.
 
Hopefully, I'll be able to report how effectively it works, or not in a
couple of weeks, when I get a chance to visit Lake Powell. I'll also try
to get some pictures of the installation.
 
Lee Shuster

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