Re: [OMC-Boats] cowling venting

From: JEFF DOOD <jdood@...>
Date: Tue, 22 Jul 2008 14:54:33 -0700

well i really don't. but, i don't have any air intake up by my stern
as you say. no intake scoops directing air to bilge. perhaps
never was, perhaps removed at some point. only intake of air into
that cowling is the small little grates in the upper back of the
compartment. that looks like the original design also. So it's
anyone's guess as to that's the original engineered design, or if i am
missing some part of the system. and my blower is not stock, it's
aftermarket. but it is located at the base of the compartment.
it's an inline blower with short 6" piece of dryer hose on the intake
side and a longer piece that goes up to the rear grates on the outflow

so ventilation issues aside, are those grills in the back of the
engine compartment enough to supply air to my spark arrestor/intake?
or am i supposed to be getting more air in there?

On Jul 22, 2008, at 10:24 AM, <tpaquette@...> wrote:

> Why do you want to cut up your cowling?
> The air intake comes from the vent in the stern. You would have to
> assume since all baots are made that way the engineers designed an
> optimal vent size and location - unless you plan to install a blower
> on the motor....
> The flame arrestor stops potential backfires from torching your
> cowling and bilge. The flame arrestor acts the same as a car
> airfilter in that it sits on top of the just is made of
> metal and funky grill layers so it wont burn....the air flows
> through it into the carb.
>> From: JEFF DOOD <jdood@...>
>> Date: 2008/07/22 Tue AM 11:34:43 EDT
>> To: "Evinrude & Johnson Boats of the 1960's and 70's"
>> <omc-boats@...>
>> Subject: Re: [OMC-Boats] cowling venting
>> AH - ok, makes sense now. although diminishing noise seems to be
>> the
>> least concern with about 1/2 the boats i see (hear) at the boat ramp
>> every time.
>> and so if the thing on top is a spark arrestor, not an air cleaner,
>> where do these engines get their air for combustion - shouldn't there
>> be an intake somewhere? not disputing, just wondering
>> so i guess i could put a grill in my cowling, and it would just be
>> louder and maybe a little less likely to explode on starting due to
>> better fume venting. but it won't run any cooler!
>> actually another question - are gas fumes heavier than air? if
>> so, where i want to put the vent won't help the fumes at all.
>> either
>> way, i always run the blower regardless.
>> On Jul 22, 2008, at 7:03 AM, D. F. Julien, AIA wrote:
>>> Hi Jeff
>>> Engine noise is probably the reason for the tight compartment. If
>>> you put a
>>> grille in the back cowling, facing forward, you'd greatly increase
>>> your
>>> awareness of the engine noise.
>>> Not that it changes your argument, but that round thing on top of
>>> the
>>> carburetor is a spark arrestor, not a filter. I guess the
>>> presumption is
>>> that boats don't go down dusty roads much during operation.
>>> -Doug Julien
>>> ----- Original Message -----
>>> From: "JEFF DOOD" <jdood@...>
>>> To: "Evinrude & Johnson Boats of the 1960's and 70's"
>>> <omc-boats@...>
>>> Sent: Tuesday, July 22, 2008 12:19 AM
>>> Subject: [OMC-Boats] cowling venting
>>>> kind of inexperienced with boat i/o motors. here's something i
>>>> don't get.......why no venting in the cowling? i happen to
>>>> have a
>>>> Deluxe, but i think it's the same story with other boats as well.
>>>> - You are supposed to vent the fumes out with a blower before
>>>> starting.
>>>> - the top of the carb has an air cleaner intake just like a car
>>>> (although small)
>>>> yet my particular cowling seals up pretty tight and seems like it's
>>>> designed to not let any air get in. it does have a smaller
>>>> grill in
>>>> the back of the engine compartment, but minimal. So why aren't
>>>> cowlings (or atleast mine) vented like crazy with air grills all
>>>> over
>>>> the place? it just seems like it would A) make the engine run
>>>> better
>>>> by providing more available fresh air intake, B) make the engine
>>>> run
>>>> even cooler with air flow taking away some of the heat , and C)
>>>> make
>>>> it easier for the accumulating fumes to get out of the cowling
>>>> without
>>>> having to rely on the blower.
>>>> I have a perfect spot right on the front of the cowling for a nice
>>>> big
>>>> chrome vent, but i don't want to be cutting any holes without
>>>> knowing
>>>> for sure first.
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Received on Tuesday, 22 July 2008

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