[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: http://www.adventurercomputer.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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Received on Sunday, 24 September 2006