Re: [OMC-Boats] timing/carb adjustment

On Wed, 30 Jul 2008, JEFF DOOD wrote:
> and in my case, (and probably all the other people who have my exact
> same boat) there are no vents at the bottom or directing things to the
> bottom.) anyone with a Johnson Deluxe wanna chime in? my
> cowling is a big bubble of fiberglass that doesn't touch the boat
> sides. i have noticed the vents on the top back rails on other
> boats the past couple days. pretty common. nothing on mine.
> makes me a little nervous. will i screw up anything to put a pair of
> the standard fin vents along the bottoms sides?

It's rare to actually see vents at the bottom - vents are place that water
can come in. Vents are usually positioned high, with pickup ducts going
down into the bilge for ventilation. The duct should end fairly low, but
above the level that the bilge pump will empty to, so they're at a point
where they can never be underwater during normal operation.

I would tend presume that the manufacturer knew what they were doing when
they designed the engine compartment. Bilge ventilation has been taken
seriously for a longtime and the Coast Guard has some pretty strict
regulations about it, though many of them were not yet in effect when our
boats were designed.

My boat (Evinrude Explorer 16) has two inlets (about 1" high by 6" wide)
in the front, just behind the rear seats, and two outlets high on the
transom, and two "vent plates" also mounted on the transom (the port one
is attached to a fuel tank overflow, the right is attached to the blower).
The inlets can be seen here:
  http://homepages.cae.wisc.edu/~brodskye/boat/boat3.jpg
and the outlets here:
  http://images.craigslist.org/010204010407010304200807291d0a6f44e66445ff52008e4f.jpg

All of these originally had duct hose connected to it, but the ducts had
all rotted out I'm uncertain as to the exact original configuration. I
recently repaired it all (dryer hose) and choose to do the following. The
bilge blower sucks from the bottom of the bilge, near the aft end (I'm
fairly sure that it originally was mounted forward). The two exhaust
outlets also suck from the bottom of the bilge using duct. The port inlet
is ducted to right next to the engine air intake, and the starboard inlet
has no duct on it at all. I've been running for several years though with
no ducting in the inlet and it didn't seem to make any difference, but I
thought I'd try to make it look nice since since I was working on it.

Anyway, I just looked at your photo and I'm not qualified to really
recommend any chances. It's difficult to believe there are no vents
at all on the compartment - the engine likely wouldn't run then. Is the
floor of the compartment recessed so it is the lowest point of the bilge?
It looks nice so I'd be hesitant to start cutting anything.

Incidentally, somebody in New Hampshire is selling a boat exactly like
mine on craigslist for $800, including a trailer.
  http://nh.craigslist.org/boa/775226896.html

Ethan

-- 
<a href="http://www.engr.wisc.edu/~brodskye/"> Ethan Brodsky </a>