[C320-list] ENGINE SPACE VENTING

[Jeff Hare]

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 running.
>>> Regards
>>> JohnM
>>> 1999#574
>> 
>