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Old 10-03-2010, 07:16   #31
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Originally Posted by YourOldNemesis View Post

Hi Jim,

Yes I am saying that you can keep the engine room temps down with a better heat exchanger. This is because the source of the heat in the engine room is the engine. If your engine room gets so hot that other components are failing then your engine cooling system is either not working properly or is under-spec'd for the job. In either case, the solution is not to add a 'blower'!

Sorry to all for the tone, I have a sarcasm problem!
So are you saying that a normal operating temperature for an engine in a large room should be different then the normal operating temperature in a small room?

I know you can't be saying that the surrounding air temperature will be same in both cases so if you are trying to lower the surrounding ambient engine room temperature you seem to be advocating 1) a change in the water cooling system to run the engine at a lower temperature when it is in a more confined space?

or

2) you are saying you just don't care about the surrounding temperature because a properly cooled engine will not get so hot as to bother other component parts that are properly speced for the job.

Is there a third choice?

Don't worry about the sarcasm problem it is endemic on the internet.

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Old 10-03-2010, 07:19   #32
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Old 10-03-2010, 07:30   #33
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Originally Posted by YourOldNemesis View Post
.....2
Well Balmar disagrees with you. They are pretty specific about the amount of engine room space they will recommend their engine mounted high output alternators have to dissipate heat without additional ventilation. While this isn't directly the engines fault if it wasn't heating up the space the alternators would have more room without ventilation so I don't see how better water-cooling can possibly make a difference here.

You can argue then to not to use that big an alternator but then your just being silly.

Jim
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Old 10-03-2010, 07:46   #34
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You've got me there! I'd suggest using one of these: HITACHI AUTOMOTIVE PRODUCTS: Water-Cooled Alternators instead!

I guess it could still be argued that if the combined heat output of your (air-cooled) alternator and your engine was heating up the engine bay too much, a higher capacity heat exchanger would reduce that engine bay temp.
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Old 10-03-2010, 07:57   #35
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Originally Posted by YourOldNemesis View Post
You've got me there! I'd suggest using one of these: HITACHI AUTOMOTIVE PRODUCTS: Water-Cooled Alternators instead!

I guess it could still be argued that if the combined heat output of your (air-cooled) alternator and your engine was heating up the engine bay too much, a higher capacity heat exchanger would reduce that engine bay temp.
But wouldn't the higher capacity heat exchanger have to reduce the engines internal operating temperature to actually make any difference? Would that be desirable in a diesel engine?

Cool water-cooled alternator by the way.

Jim
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Old 10-03-2010, 07:59   #36
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Originally Posted by forsailbyowner View Post
The last time I was boarded and inspected the coast guard officer asked me to turn on bilge blower as part of his inspection. ?required?
I could only find mandatory forced ventilation requirements if you have a gasoline engine under 33 CFR 183.610.

http://www.access.gpo.gov/nara/cfr/w...cfr183_99.html


Outside of what you are asking, its good common sense to have a bilge blower regardless of what types of fuel you have on board.

Were you cited for not having a working bilge blower?
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Old 10-03-2010, 08:11   #37
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But wouldn't the higher capacity heat exchanger have to reduce the engines internal operating temperature to actually make any difference?
Wow, I don't know!
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Old 10-03-2010, 08:40   #38
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Manufacturers are required to install bilge blowers.
OOPS, I got caught in Davids's editing.

On GASOLINE POWERED Vessels.

The United States Coast Guard's mandatory requirements for ventilation for boats with gasoline engines for propulsion or auxiliary machinery are found in 33 CFR, Subpart K, Sections CFR 183.601 - 183.630. Refer to the CFR for complete, current federal requirements.

Additionally, see ABYC H-2, Ventilation of Boats Using Gasoline.

In addition to Natural Ventilation (required), these standards require Powered Ventilation (at least 1 Blower per Gas Engine).

***

ABYC Standard H-32
Ventilation Of Boats Using Diesel Fuel states:
"power or natural ventilation is not required on a diesel boat, but may be used to control compartment temperature." The standard also provides guidance on other ventilation considerations such as supplying necessary combustion air, venting hydrogen gas from batteries when appropriate, and removing the discharge from fixed gaseous fire extinguishing systems.

ABYCís "Ventilation Compliance Guideline" (#COMP005, 64 pages, Ī $120) guides you through the calculations for net compartment volume and ventilation system design. Covers powered and natural ventilation, as well as ventilation of fuel tank compartments and determining blower system output.

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Old 10-03-2010, 08:54   #39
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My engine compartment exhaust blower just quit. Burned out. Doesn't seem to make any difference. Seems to me the diesel itself is continuously exhausting from 50 to 10 CFM just running. Why would I need a little more?
(But sometimes I do warm my hands by the outlet)
daddle:

Replace the blower fan.

One of the (MANY) reasons to provide an Exhaust Fan is to ensure a slightly negative air pressure in the engine compartment (relative to the living space). This ensures that pollutants donít migrate from engine rm. to cabin.
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Old 10-03-2010, 13:12   #40
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I thought this thread was aboot ventilation of the engine spaces....

Getting rid of hot air in the engine compartment makes for a more comfortable below deck atmosphere....in some boats.
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Old 10-03-2010, 13:57   #41
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Engine heat prewarms the bunk in winter in my aft cabins, not so nice in the summer though.
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Old 10-03-2010, 14:26   #42
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daddle, when all is said and done do you think the cheap misers who built your boat would have wasted money on a blower unless they felt it was necessary for some reason?

And yes, in fact, you'll find that high performance engine builders routinely use finned valve covers and finned oil pans on engines. The reason being to COOL THE OIL. An internal combustion engine is actually cooled by the oil film in the cylinder walls, and the oil is cooled by the water. Let that oil get too hot, at any point, and it breaks down and forms coke, tar, sludge. Which eventually cause it to stop lubricating, or plug the cooling passages and cause a rather sudden engine failure.

When you shut down an engine there's no cooling system and the oil now takes on the entire heat load, cooking itself off. Fins on the valve covers and all will help cool the oil sooner, but running an external blower will lower the engine room temperature, the engine temperature, the engine OIL temperature. Giving you better engine life, better oil life, and a cooler main cabin sooner.

So yes, there's a reason to have a blower, and to actually run it after you shut down, until the engine block temps have dropped enough so your oil is no longer cooking in the head or anyplace else.
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Old 10-03-2010, 14:38   #43
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daddle:

Replace the blower fan.
Yeah, you and hellosailor are mostly correct. I'll replace the blower so I can run it after shutdown. But the original post was that the engine itself is a bigger blower than the electric one. The engine draws more air, I think, thru the engine area for free than the blower ever will. I figure the diesel is pumping 35CFM, changing the compartment air in under a minute. Plus the blower sucks up 5AH which I'd rather went to the batteries. Cheers.
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Old 10-03-2010, 18:07   #44
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For alternator cooling just put a thermostat on the vent fan and take the power supply from the alternator itself. It will only run when the ignition is on and the alternator is producing. Just be sure there is no twelve volts when the ignition is off, there shouldn't be but -.
With mono's or low mounted engines the air vent pipes, in and out of the engine compartment need to be water proof in storm conditions. The diesel engine is pretty water proof, except for the engine intakes, but electricals will suffer, and water could build up in the bilges. [How simple life is with a single engined CAT!]
If the engine compartment gets hotter after stopping the engine then again a thermostat tripped fan will help to remove the warmed air. Just be sure HOT parts are not close to wood or GRP. A metal shield (ally prefered) with air gap both sides will protect any areas that look scorched. Older boats often carry non-vendor mods that may not have been properly considered. Scorching is a very clear WARNING that things are getting TOO HOT.
The other engine protection device, and indicator of too high a power demand, is oil temperature (not often seen on boats). Oil temperature (not water temp) needs to be above 60 and below 110 deg C [140 to 220 deg F] in normal use, with the temps above these beginning to stress the engine lube system. Giving the engine a warm up run until temps start to climb is also a good way of keeping the oil good and extending the life of the engine.
The minimum temps are to purge water (condensation etc) from the lube oil, and the max. to prevent the oil breaking down. Your engine supplier will have the correct figures.
It's a good indication in stressful situations of just how hard you are working the engine. Adding oil cooling is easy using standard car type components and methods for air cooling if the compartment doesn't get too hot itself.
Hope this helps. It's just as important in pre-adventure shake down as the rigging.
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Old 10-03-2010, 19:20   #45
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Cool My Take on the Intake, Before the Topic is Exhausted

Run the blower to create slightly negative pressure in engine compartment (which in my vessel is smack in the middle of the saloon) so that diesel smells do not enter living areas? Check.

Run blower to keep my high-output alternator cooler, extending its life/increasing its reliability? Check.

Run blower during and after engine use to remove heat radiated by the normal functioning of the engine, in order to keep my saloon more comfortable? Check.

Run blower because the cooler intake air is denser and slightly increases the power output of my engine?

Well, the effect is small, but technically a benefit, so, yeah, check.

Those of you who think the question includes the idea of using a blower as a viable way of actually affecting the operating temperature of the engine (instead of controlling the effects of the engine's normal radiant heat on engine space components and living areas) aren't understanding the question, IMHO.
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