Re: [OMC-Boats] OMC-Boats Digest, Vol 15, Issue 20

I have a 1969 Sportsman 120, and I'am in the process of fixing the engine compartment doors. The question I have is what does the section look like between the doors and what is right under it. All I have is what it in a computer picture.

> From: omc-boats-request@...
> Subject: OMC-Boats Digest, Vol 15, Issue 20
> To: omc-boats@...
> Date: Tue, 22 Jul 2008 14:30:42 -0400
>
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> Today's Topics:
>
> 1. Re: cowling venting (Douglas F. Julien, AIA)
> 2. Re: cowling venting (Douglas F. Julien, AIA)
> 3. Re: cowling venting (tpaquette@...)
> 4. Engine compartment venting (mckeown)
> 5. Re: Engine RPM and Boat Speed. (Lee Shuster)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Tue, 22 Jul 2008 11:20:24 -0500
> From: "Douglas F. Julien, AIA" <dfjulien@...>
> Subject: Re: [OMC-Boats] cowling venting
> To: "Evinrude & Johnson Boats of the 1960's and 70's"
> <omc-boats@...>
> Message-ID: <000201c8ec17$13b9b640$6302a8c0@...>
> Content-Type: text/plain; charset="iso-8859-1"
>
> Hi Jeff
>
> The spark arrestor, actually a backfire flame arrestor, is also the air
> intake - there's just no replaceable filter involved. It's required by the
> Coast Guard on all boats with an engine that could backfire, which, besides
> being noisy, shoots flames out of the carburetor.
>
> Gas fumes are heavier than air - which is why the blower intake is at the
> bottom of the bilge and why the scoops have 3" hoses directing the incoming
> air to the bottom of the bilge when underway. Explosions seem to be rare
> and probably involve a fuel leak with lots of gas sloshing around down
> there - any experience in this group? (!)
>
> The rumble of that oddfire V6 with the tilt up a little brings a smile to my
> face every time...
>
> -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 10:34 AM
> 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.
> > >>
> > >>
> > >>
> > >> _______________________________________________
> > >> OMC-Boats mailing list
> > >> OMC-Boats@...
> > >> http://lists.ultimate.com/mailman/listinfo/omc-boats
> > >
> > > _______________________________________________
> > > OMC-Boats mailing list
> > > OMC-Boats@...
> > > http://lists.ultimate.com/mailman/listinfo/omc-boats
> >
> > _______________________________________________
> > OMC-Boats mailing list
> > OMC-Boats@...
> > http://lists.ultimate.com/mailman/listinfo/omc-boats
>
>
>
> ------------------------------
>
> Message: 2
> Date: Tue, 22 Jul 2008 11:20:24 -0500
> From: "Douglas F. Julien, AIA" <dfjulien@...>
> Subject: Re: [OMC-Boats] cowling venting
> To: "Evinrude & Johnson Boats of the 1960's and 70's"
> <omc-boats@...>
> Message-ID: <000201c8ec17$0dbc3420$6302a8c0@...>
> Content-Type: text/plain; charset="iso-8859-1"
>
> Hi Jeff
>
> The spark arrestor, actually a backfire flame arrestor, is also the air
> intake - there's just no replaceable filter involved. It's required by the
> Coast Guard on all boats with an engine that could backfire, which, besides
> being noisy, shoots flames out of the carburetor.
>
> Gas fumes are heavier than air - which is why the blower intake is at the
> bottom of the bilge and why the scoops have 3" hoses directing the incoming
> air to the bottom of the bilge when underway. Explosions seem to be rare
> and probably involve a fuel leak with lots of gas sloshing around down
> there - any experience in this group? (!)
>
> The rumble of that oddfire V6 with the tilt up a little brings a smile to my
> face every time...
>
> -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 10:34 AM
> 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.
> > >>
> > >>
> > >>
> > >> _______________________________________________
> > >> OMC-Boats mailing list
> > >> OMC-Boats@...
> > >> http://lists.ultimate.com/mailman/listinfo/omc-boats
> > >
> > > _______________________________________________
> > > OMC-Boats mailing list
> > > OMC-Boats@...
> > > http://lists.ultimate.com/mailman/listinfo/omc-boats
> >
> > _______________________________________________
> > OMC-Boats mailing list
> > OMC-Boats@...
> > http://lists.ultimate.com/mailman/listinfo/omc-boats
>
>
>
> ------------------------------
>
> Message: 3
> Date: Tue, 22 Jul 2008 13:24:34 -0400
> From: <tpaquette@...>
> Subject: Re: [OMC-Boats] cowling venting
> To: "Evinrude & Johnson Boats of the 1960's and 70's"
> <omc-boats@...>, "Evinrude & Johnson Boats of the
> 1960's and 70's" <omc-boats@...>
> Message-ID:
> <20080722172434.BXJC13398.ispmxmta05-srv.windstream.net@...ltel.net>
>
> Content-Type: text/plain; charset=ISO-8859-1
>
> 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 carb....it 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.
> > >>
> > >>
> > >>
> > >> _______________________________________________
> > >> OMC-Boats mailing list
> > >> OMC-Boats@...
> > >> http://lists.ultimate.com/mailman/listinfo/omc-boats
> > >
> > > _______________________________________________
> > > OMC-Boats mailing list
> > > OMC-Boats@...
> > > http://lists.ultimate.com/mailman/listinfo/omc-boats
> >
> > _______________________________________________
> > OMC-Boats mailing list
> > OMC-Boats@...
> > http://lists.ultimate.com/mailman/listinfo/omc-boats
> >
>
>
>
> ------------------------------
>
> Message: 4
> Date: Tue, 22 Jul 2008 12:23:20 -0500
> From: "mckeown" <mckeown@...>
> Subject: [OMC-Boats] Engine compartment venting
> To: <omc-boats@...>
> Message-ID: <002001c8ec1f$a395bd60$eac13820$@...>
> Content-Type: text/plain; charset="us-ascii"
>
> Running the blower while underway is unnecessary if your factory venting
> system in intact. The original venting was designed to meet USCG specs. My
> '71 has two rear-facing vents with long 3" hoses attached. These hoses run
> to the bottom of the bilge so that whenever the boat is in forward motion,
> any fumes are being pulled out of the boat.
>
>
>
> There are also two forward-facing air intakes that supply air for cooling
> and combustion to the engine compartment. Any addition of grilled openings
> would only increase noise; you'd see no change at all in engine cooling or
> performance. Remember, unlike a car where all waste heat comes out of the
> radiator and through the engine compartment, waste heat in our boats goes
> into the lake!
>
>
>
> Bob
>
>
>
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> ------------------------------
>
> Message: 5
> Date: Tue, 22 Jul 2008 12:30:33 -0600
> From: "Lee Shuster" <lee.k.shuster@...>
> Subject: Re: [OMC-Boats] Engine RPM and Boat Speed.
> To: "Evinrude & Johnson Boats of the 1960's and 70's"
> <omc-boats@...>
> Message-ID:
> <8D0B9A86CFFA8A4AB3DAD5FD05114B48D7965B@...>
> Content-Type: text/plain; charset="us-ascii"
>
> I left out a couple of important points:
>
> 1) Assumption A: I assume you have accurately measured your "true"
> speed. Using a GPS or an accurately measured and marked-off course?
> Verify the Pitot is accurate or not partially obstructed. (My experience
> is they are surprisingly accurate - but still check/verify.)
>
> 2) Observation B: Something is way off here. Your boat with a 90 hp
> engine would top 30+ mph new, lightly loaded. Either your V6 is only
> hitting on 3 cylinders, or there is literally a ton of weight or maybe a
> ton of barnacles or some combination of all three?
>
> 3) Observation C: Your observed engine RPM of 3700 is not allowing the
> engine to deliver it's peak horsepower. Could be many reasons for that.
> I'd start by incrementally dropping your prop pitch, 18", 16" 14" 12"
> until your can achieve 4300-4500 RPM at WOT (Wide Open Throttle). The
> SST (Stainless Steel props are more efficient (less flex) and are
> available in add pitches (19, 17, 15, 13). The best running props are
> in the middle pitch ranges, not the extremes.
>
> 4) Probably not a bad idea to weigh the boat/trailer on a public scale,
> take out as much junk as possible, and unhook from tow vehicle.
>
> ________________________________
>
> From: omc-boats-bounces@...
> [mailto:omc-boats-bounces@...] On Behalf Of Lee Shuster
> Sent: Tuesday, July 22, 2008 9:22 AM
> To: Evinrude & Johnson Boats of the 1960's and 70's
> Subject: Re: [OMC-Boats] Engine RPM and Boat Speed.
>
>
> I have a online website calculator that you can plug in variable data:
> http://hhscott.com/evinrude/docs/BSLAC.htm
>
> the calculator takes several variables into consideration and calculates
> a THEORETICAL top speed. It has been verified against factory published
> information and in the real world using my 1966 Sportsman with both the
> Buick V6 and the Chevy V8.
>
> Here's what I come up with for your boat (making assumptions that may
> not be right):
>
> Since 3700 RPM is OVER PITCHED for your power-to-weight ratio, you
> either are down on power or up on weight. For this calculation we will
> assume a little of both.
>
> HP -- 140 hp
> Empty Hull Weight: 1975 lbs
> Crew Weight: 2 @... 170 lbs ea
> Fuel and Gear: 16 gal Fuel @... 7 lbs/gal = 112 lbs, plus 58 lbs misc
> safety gear
> Altitude Above Sea Level : 1000' ASL
> Hull Eff Factor = 175 (constant factor verified for a clean, smoothly
> waxed 1964 - 1968 16ft E/J 16 ft Tri-hull)
>
> The Calculated Result: 34 mph
>
>
> So to drop another 9 mph you have to add quite a bit more weight, and/or
> be at a higher altitude, and/or have a "dirty" hull, and/or being
> carrying more passengers, and/or be producing less power.
>
> (Factory specs say your boat, with 1 crew and half a tank of fuel at Sea
> Level would do about 39 mph on an AL 14x18 prop at around 4300 RPM.)
>
> Have fun punching in your own data. I suspect weight is your enemy (but
> that alone should not bring you down that bar), possibly also look at
> your engine and prop combo and then clean and wax that hull.
>
> Lee Shuster
> Salt City - Utah
>
>
>
>
>
> ________________________________
>
> From: omc-boats-bounces@...
> [mailto:omc-boats-bounces@...] On Behalf Of Don Mandelas
> Sent: Tuesday, July 22, 2008 1:12 AM
> To: Evinrude & Johnson Boats of the 1960's and 70's
> Subject: Re: [OMC-Boats] Engine RPM and Boat Speed.
>
>
> I have a 1967 Evinrude Sportsman boat with the V-6 155 hp engine. On
> the stern drive unit I have installed the 14 x 18 propeller. When the
> engine reaches 3700 RPMs how fast generally should I be traveling across
> the water? It seems lately that I am going slower than normal (about 25
> mph).
>
> ________________________________
>
> Stay in touch when you're away with Windows Live Messenger. IM anytime
> you're online.
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>
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>
> End of OMC-Boats Digest, Vol 15, Issue 20
> *****************************************

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Received on Wednesday, 23 July 2008