Maybe I misunderstand but are you asking about the little round ones close
to the sole?
I don't know where to find them but if that is all the venting for that
engine box, your engine will not get enough air.
It would not be sufficient for a gas engine but diesels need twice the air
of a gas engine.
There should be large louver vents on the front or side of the engine cover.
If that is not possible esthetically, you may want a blower that sends air
in the bilges.

PS: engine installations where my primary business for 10 years.


--
Jacques
http://www.bateau.com



"Gary Warner" wrote in message
...

I've asked a few times if anyone knows where to get vents like
these, but this time I actually have a link to pictures - so that
may help.

These are pictures of an engine cover on a boat similar to ours.

http://www.shutterfly.com/osi.jsp?i=...21b321e102454c

Thanks!
Gary

"Jacques Mertens" wrote in message
...
It would not be sufficient for a gas engine but diesels need twice the air
of a gas engine.
If the two engines are of equal capacity and turning at the same speed and
both are say four stroke engines then why would diesel require twice the
amount of air?

Compression ratio.

"L & D milligan" wrote in message
...

"Jacques Mertens" wrote in message
...
It would not be sufficient for a gas engine but diesels need twice the
air
of a gas engine.
If the two engines are of equal capacity and turning at the same speed and
both are say four stroke engines then why would diesel require twice the
amount of air?

"Jacques Mertens" wrote in message
news
Compression ratio.


Makes sense. But wouldn't the higher compression ratio of diesels be at
least partially offset, if not completely, by their significantly lower
operating RPM's when compared to gas engines? Seems between these two
offsetting factors, air consumption should be pretty close to the same given
similar displacement and operating duties. Just thinking out load.

It has nothing to do with compression ratio actually. The amount of air is
increased because a diesel has no throttle blade nor is any measurable
amount of manifold vacuum created. A diesel of say 400 cubic inches uses
the same air a gas engine of 400 cubic inches would if it were run wide open
100% of the time.

--
Steve
=======================
Remove the not dot from my address to abuse my email box
"L & D milligan" wrote in message
...

"Jacques Mertens" wrote in message
...
It would not be sufficient for a gas engine but diesels need twice the
air
of a gas engine.
If the two engines are of equal capacity and turning at the same speed and
both are say four stroke engines then why would diesel require twice the
amount of air?

But you would need to size vents for full throttle anyway ....
I think we are all guessing so far ....

I'd have thought a "gas" ( petrol in this part of the world ) engine might
have been less forgiving of pressure drop through the vents. Or it might be
something to do with cooling?
David


"Steve Barker" wrote in message
...
It has nothing to do with compression ratio actually. The amount of air
is
increased because a diesel has no throttle blade nor is any measurable
amount of manifold vacuum created. A diesel of say 400 cubic inches uses
the same air a gas engine of 400 cubic inches would if it were run wide
open
100% of the time.

--
Steve
=======================
Remove the not dot from my address to abuse my email box
"L & D milligan" wrote in message
...

"Jacques Mertens" wrote in message
...
It would not be sufficient for a gas engine but diesels need twice the
air
of a gas engine.
If the two engines are of equal capacity and turning at the same speed
and
both are say four stroke engines then why would diesel require twice the
amount of air?

On Wed, 9 Jul 2003 10:05:14 -0400, "Jacques Mertens"
wrote:

Maybe I misunderstand but are you asking about the little round ones close
to the sole?
I don't know where to find them but if that is all the venting for that
engine box, your engine will not get enough air.
It would not be sufficient for a gas engine but diesels need twice the air
of a gas engine.
There should be large louver vents on the front or side of the engine cover.
If that is not possible esthetically, you may want a blower that sends air
in the bilges.

PS: engine installations where my primary business for 10 years.

Aren't you puzzled by your observance that Chris-Craft designed an
engine box which would prevent an engine from running?

Actually, the engine is not totally dependent on these small vents for
air for the engine. The engine box is not somehow hermetically sealed
to the floorboards. Many, if not most, runabouts have no holes in
the engine box. In a runabout the air flows from the bow of the boat
to the rear. Typically, a runabout has a forward facing vent on the
foredeck. This vent typically has a tube underneath it which extends
to the bilge. Also, the area between the dashboard and the upper
floorboards (placed at a roughly 45 degree angle) is almost always
open on a runabout. Usually, a runabout will have another set of
forward-facing vents at the forward end of the engine compartment. On
a "utlity" type of boat (engine in a box) like Mr. Warner's, these
vents are on the side decks. These vents have a tube underneath also.
On the rear deck there will be two aft facing vents. These have no
tubes. The whole idea is, of course, to promote air circulation low in
the bilge so that explosive vapors do not accumulate. Most runabouts
are designed so that there is nothing to impede air flow in the bilge
from stem to stern.

Air supply for the engine comes to some extent from the air flow
provided by this on deck vent arrangement. However, I suppose most air
for the engine comes from the bilge area. And the main supply for this
area is the space between the dashboard and floorboards forward.

My guess is that the vents on Mr. Warner's Sea Skiff are there largely
for style considerations. Some Sea Skiffs have a plywood "bulkhead"
forward of the dashboard which goes from keel to deck. If this Sea
Skiff has this bulkhead, the additional vents on the box might
actually be providing additional marginal air supply. However, a Sea
Skiff has steam bent frames. There will always be a opening for air
circulation between these frames where the floorboards meet the hull
sides.

Chris-Craft would not design a boat in which the engine was sealed so
that it would not run.

I hope not but not would bet too much on it.
I saw at least two production boats from major companies that had such a
flaw.
The 1st was an Elvstrom designed sailboat with a Volvo in the saloon, under
the table. It counted on air from the bilges to run and died after 10
minutes unless you opened the box.
The other one was a sportfishing boat in the 40' range. The owner wondered
why with the same engines he could not go as fast as the other boats in his
category. During a sea trial, I noticed that you could not open the engine
hatches: they were sealed tight from the vacuum! I wedged a piece of 2x4
under the hatch and the boat ran 5 knots faster!

That Chris-Craft may very well have been designed for a gas engine that does
not require as much air.
Anyway, I was just trying to help.

--
Jacques
http://www.bateau.com

"P.C. Ford" wrote in message
...

Chris-Craft would not design a boat in which the engine was sealed so
that it would not run.