[C320-list] ENGINE SPACE VENTING

[John morrison]

I’ve never had an issue with engine power on my boat, despite the crushed, altogether too small dryer vent hoses, and never turning on the blower! I am taking out the hoses and will leave the holes to atmosphere in the stern. I expect to get better performance from the refrigeration unit. I can report on any observed changes in the fall…if I think of it!
Regards
JohnM
1999#574
> On Mar 17, 2018, at 7:05 PM, John Frost <john at frostnet.net> wrote:
> 
> WOW! Actual facts that we can use. Great research job Don
> 
> Thanks,
> John
> 
> John C. Frost
> President
> Safety Engineering Services, Inc.
> 2627 Trailway Rd.
> Huntsville, AL 35801
> (256) 650-0335
> 
> -----Original Message-----
> From: C320-list [mailto:c320-list-bounces at lists.catalina320.com] On Behalf
> Of Donald Lawson
> Sent: Saturday, March 17, 2018 5:14 PM
> To: C320-List at Catalina320.com
> Subject: Re: [C320-list] ENGINE SPACE VENTING
> 
> Jeff & Graeme
> Rather than have a debate, I thought I would give all the data I could
> collect and let everyone make their own decision as to use/removal of the
> blower Some of you will have to convert to english/metric where I did not.
> Also, this is for a 3YM30 Yanmar only but I expect it applies somewhat to
> all diesels.
> 
> This 66 cu in (1.115 l) engine needs air at about 50 cu ft/min at 3000 rpm..
> Assumes a .9 volumetric efficiency for this engine (under 1000 hours).
> Older diesels are above or near .8.
> 
> Per the Yanmar Installation Manual (not owners manual):  1) Maximum engine
> room Temp shall be 140 deg F (60 C) and 2) Minimum Engine Room Ventilation
> Fresh Air Exchange
>    (Ventilator Capacity) shall be 194 cu ft/min (5.5 cu meters/min).
> 
> Per Yanmar Installation Manual horsepower decreases from 30 to 29, at rated
> rpm,  when temp at the fuel pump increases from 25 C to 40 C. Expect lower
> hp at 60C.
> 
> Rule and Shurflo ventilators have about 250 Cu ft/min capacity with a 4in
> hose.  I think I have a 4in dryer hose crushed to 2 in.
> 
> ABYC Diesel Ventilation Standard H-32, from 1987, states:
> H-32.4.
> PURPOSE
> These recommended practices and engineering standards establish requirements
> for ventilation of boats using diesel fuel.
> SCOPE
> These recommended practices and engineering standards apply to boats using
> diesel fuel only for electrical generation, mechanical power and propulsion.
> NOTE:	Ventilation requirements for boats using gasoline as fuel are
> contained in ABYC H-2, "Ventilation ofBoats Using Gasoline".
> DEFINITION
> Ventilation - The changing of air within a compartment by natural or
> mechanical means. Ventilation may be effected by dilution of contaminated
> air, by introduction of fresh air, or by local exhaust of contaminated air.
> REQUIREMENTS -IN GENERAL
> a Ventilation Principle - Ventilation cannot be relied upon to remove all
> vapors that are pos- sible from the presence of liquid fuel resulting from
> fuel system failures or fuel spillage. (See ABYC H-33, "Diesel Fuel
> Systems") b Storage Batteries - Compartments containing storage batteries
> shall be vented to provide for the escape of hydrogen in accordance with
> ABYC E-lO, "Location and Installation of Storage Batteries".
> c Diesel Fuel Vapors - Due to the characteristics of diesel fuel and the
> closed nature of the diesel engine fuel system, neither mechanical nor
> natural ventilation, as prescribed for gasoline powered vessels, is
> necessary to remove diesel fuel vapors. (See ABYC H-2, "Ven- tilation of
> Boats Using Gasoline") d Removal of Fixed Gaseolls Fire Extinguishing System
> Discharge - Ventilation means shall be provided to remove the discharge from
> ftxed gaseous ftre extinguishing systems.
> e Combustion Air - Ventilating provisions and openings to the machinery
> space provided for supplying combustion air shall accomodate the air
> requirements required by the engine manufacturer(s) for each propulsion and
> auxiliary engine in that space. These openings may also function as means of
> providing natural ventilation.
> f Additional Uses of Ventilation - Power or natural ventilation is not
> required on a diesel boat, but may be used to control compartment
> temperature. power ventilation may also be used in the machinery space for
> odor control and personnel comfort while servicing equipment.
> 
> Note c and e above.   Could not find the current standard without paying
> money, expect it to be unchanged?
> 
> Based on the above the blower is not there to cool the engine but does
> exchange air for engine room cooling and combustion. 
> 
> Therefore I will:
> Continue to run my blower during engine operation per Yanmar's requirement. 
> Change the dryer hose to something more substantial to keep it from being
> crushed when I work in the aft areas.
> Install an electric head
> 
> Happy Boating
> Don Lawson
> 
> 
> 
> 
> 
> On Mar 15, 2018, at 2:09 PM, Jeff Hare wrote:
> 
>> Don,
>> 
>> Per what Graeme said, that's how ours was configured as well from the
> factory.  For a bilge blower to really serve its intended purpose, it would
> have to suck air in and vent it outside, as it's supposed to remove residual
> flammable "gasoline" fumes prior to starting the engine to prevent awesome
> dockside entertainment.  
>> 
>> So, if you really run the blower when you run the engine, that probably
> only serves to validate the point that the engine gets what it needs just
> fine through many places like the front and aft engine cover cracks, all the
> places where hoses and bilge drain holes exist in addition to the pair of 4"
> holes.
>> 
>> So, generally no need to sweat this.  To my knowledge I've never heard 
>> of a 320 having overheating or efficiency issues due to the way the it 
>> was installed by the factory.  On the bonus side, without the bilge 
>> blower hoses clogging up the transom vent holes, your fridge might run 
>> a little cooler.  :)
>> 
>> There's really nothing stopping you from drilling another 3" or 4" vent
> hole near the existing ones to increase air flow except that you'd be hard
> pressed to show made any measurable difference.
>> 
>> Cheers!
>> -Jeff
>> 
>> -----Original Message-----
>> From: C320-list <c320-list-bounces at lists.catalina320.com> On Behalf Of 
>> Graeme Clark
>> Sent: Thursday, March 15, 2018 5:20 AM
>> To: Catalina list <C320-List at Catalina320.com>
>> Subject: Re: [C320-list] ENGINE SPACE VENTING
>> 
>> Don
>> 
>> I may be being stupid, but cant see how running the blower improves the
> airflow *to* the engine? It sucj=ks air away from the engine and is pretty
> inefficnet at that according to Jeff). The suction from the air intake on
> the engine itself when the piston is drawing in air probaly exceeds the
> suction from the blower by a factor of about 50 at a guess.
>> 
>> Only if your blower was reversed to pump air INTO the engine compartment
> would any possible benefit be accrued, surely?
>> 
>> Just a thought
>> 
>> Graeme
>> #366
>> 
>>> On 15 Mar 2018, at 04:26, Donald Lawson <dnclaws at aol.com> wrote:
>>> 
>>> IMO.
>>> When I rebuilt/ replaced my engine(s) I learned a lot about the Amount of
> air a Diesel needs to run.  It needs a lot of cold air to run efficiently. 
>>> I run the blower while the engine is running, not to cool the engine, but
> to ensure that I provide the engine with enough cool combustion air. 
>>> I agree with Jeff that the blower is not used for cooling the engine 
>>> although I don't quite agree about better paths of air for engine run.
>>> My aft cabin mattress pretty much precludes that. HOWEVER If you 
>>> removed the hoses there may be enough SQ area of opening to get rid of
> them.  Will do the math and get back to ya'll, but I seem to remember a 3in
> dia hole is enough for a 2GM20.  We have 2, so may not be an issue.  I will
> rid myself of them in the future. I pretty much crushed them working on the
> fridge anyway.
>>> Don Lawson
>>> #1104
>>> On Mar 14, 2018, at 4:35 PM, Jeff Hare wrote:
>>> 
>>>> Not to be critical of anyone's answers, because it's great to bounce
> these thoughts around to help refine your logic, but seriously don't
> over-think this.  
>>>> 
>>>> The engine doesn't need cool ambient air to keep it cool, that's what
> the raw water heat exchanger is all about. Otherwise they would not put it
> in an insulated box with a couple lengths of dryer hose.  It also doesn't
> need any duct work to feed it air to run because there are SO many better
> paths for hull-cooled bilge air to get into the engine that it's simply a
> non-issue.
>>>> 
>>>> If you really believe that the blower reduces the heat in the aft cabin
> with the stock hoses, awesome, but it really doesn't.  No way you're moving
> that much heat out through those crinkled half crushed hoses with our anemic
> blower. LOL!  You'd have to run the blower till the engine block cools down
> quite a bit to make any real difference or it'll just reheat the air again.
> By then someone sharing the mooring field with you would have launched a
> torpedo at your boat because of all the racket that thing produces.
>>>> 
>>>> If you really want to help remove any excess aft cabin heat, I'd suggest
> that you open the aft cabin access door at the foot of the bed and aft
> cockpit locker above the fridge compressor and let convection take over.  If
> you really wanted to use hoses for some reason, you'd need 4" smooth wall
> hoses that have fewer bends and a more powerful blower to actually get any
> reasonable airflow.
>>>> 
>>>> I'm pretty certain that the blower and the hoses were only installed to
> satisfy outdated requirements for a bilge blower (which diesels are exempt
> from now in the US anyway).
>>>> 
>>>> Cheers!
>>>> #809   stay'n hoseless  :)
>>>> -Jeff Hare
>>>> 
>>>> -----Original Message-----
>>>> From: C320-list <c320-list-bounces at lists.catalina320.com> On Behalf 
>>>> Of John Meyers
>>>> Sent: Monday, March 12, 2018 3:23 PM
>>>> To: C320-List at catalina320.com
>>>> Subject: Re: [C320-list] ENGINE SPACE VENTING
>>>> 
>>>> John
>>>> 
>>>> If thing for convection to work you may need one of the openings to be
> connected to a hose with one end lower than the one without a hose. The one
> with the hose will let cold/fresh air in when the hot air rises to the vent
> without the hose.
>>>> 
>>>> John Meyers (The other John M)
>>>> 
>>>> On Mon, Mar 12, 2018 at 10:08 AM, John morrison 
>>>> <sail-ability at sympatico.ca>
>>>> wrote:
>>>> 
>>>>> I attended a surveying seminar on the weekend, and for those who 
>>>>> may not know ( I didn't) diesel engine spaces do not require forced 
>>>>> ventilation in order to pass a survey. You may want to have it for 
>>>>> other reasons as has been mentioned in this forum. I intend to 
>>>>> remove the vent hoses from the cowls and let the space vent by
> convection.
>>>>> The cowls are high up in the stern so warm air should exit pretty 
>>>>> well, we'll see  how that works. When the hoses are attached the 
>>>>> cowl holes are blocked and hot air from the engine, fridge 
>>>>> compressor, cannot escape; unless of course the blower is r
> 
> 
>