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Old 23-07-2012, 10:20   #16
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Re: Engine room ventilation

Simply put, you need the amount of intake air specified for your diesel at wide open throttle. The exhaust fan can be run continuously or just when you wqant to turn it on. The engine is a much bigger stronger air pump than any exhaust fan you can buy, but add the amount of ventilation area needed for it also. A couple large cut holes in the inside of the coaming/cockpit, in an out of the way area, with a clam shell cover might do it....
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Old 25-07-2012, 06:03   #17
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Re: Engine room ventilation

See also ➥ Engine Ventilation: Skip it?

And ➥ Engine Room Blower
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Old 25-07-2012, 10:59   #18
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Re: Engine room ventilation

I might add , I had ventilation on two of my boats, and found the heat to be reduced noticeably after a long motoring session if I ran the fan the last hour or so before getting to port.... if not the whole time. The whole engine compartment becomes a big "space heater" after a long haul and especially in a calm anchorage... hot for hours....
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Old 25-07-2012, 11:27   #19
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Re: Engine room ventilation

The only time I tend to use the blower is during my Delta trip every year in August. It's hot up there, and when I get back into the sloughs I'm motoring most of the time. I'm less concerned with cooling the engine room than keeping its heat out of the rest of the boat.

On most modern production boat the engine is drawing air from the bilges. I don't see this as a big concern because there are plenty of spaces for air to get into the bilge, starting with the mast on keel-stepped boats.
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Old 25-07-2012, 12:11   #20
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Re: Engine room ventilation

You gotta have a goesin and a goesout...
Use TWO dorade vents. One pointed forward the other aft..
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Old 26-07-2012, 10:56   #21
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Re: Engine room ventilation

Quote:
Originally Posted by Cheechako View Post
I might add , I had ventilation on two of my boats, and found the heat to be reduced noticeably after a long motoring session if I ran the fan the last hour or so before getting to port.... if not the whole time. The whole engine compartment becomes a big "space heater" after a long haul and especially in a calm anchorage... hot for hours....

Im with this guy. I run my blower any time the engine is on and for a good while afterwards sometimes an hour or more after a long motore. I run it till the air blowing out aint warm anymore. Makes a huge difference in the temps below decks. Otherwise as has been mentioned the engine and its coolant are just a big heat sink that will radiate heat out to the rest of the boat until there isnt any left to radiate.
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Old 26-07-2012, 11:03   #22
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Re: Engine room ventilation

[QUOTE=Bash;998385]The only time I tend to use the blower is during my Delta trip every year in August. It's hot up there, and when I get back into the sloughs I'm motoring most of the time. I'm less concerned with cooling the engine room than keeping its heat out of the rest of the boat.

On most modern production boat the engine is drawing air from the bilges. I don't see this as a big concern because there are plenty of spaces for air to get into the bilge, starting with the mast on keel-stepped boats.[/QUOTE]

Only if the mast has alot of holes down there! Isnt the base usually blocked? Also, it's a very big chimney sucking air if it's not.......hmmm... good idea here, bore a 2" hole attach a duct/hose routed to the engine compartment and let the mast chimney effect suck out the air! a 40-60 ft chimney will suck more than a bilge blower!
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Old 14-11-2016, 15:43   #23
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Re: Engine room ventilation

You might be able to find a solution here: JEC Marine who supply dc brushless marine engine room fans: www.jecmarine.com
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Old 26-11-2016, 15:17   #24
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Re: Engine room ventilation

Send me a PM and I will email a copy of a magazine article I wrote for designing and building an engine "hush box" which includes intake and exhaust blowers.

I always ran the exhaust blower for 15 minutes after engine shut-down to rid the hush box of excess heat. A simple wind-up kitchen timer let me know when time was up.
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Old 26-11-2016, 22:27   #25
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Re: Engine room ventilation

You can measure the pressure difference between the engine room and ambient using a water manometer (a long vinyl tube with water in it with a few inches of air left at each end). You put one end in the engine room, and fix the other end outside such as in the cabin - of course making sure the ends of the tube are approximately the same height, otherwise the water will drain out :-). Then, make a note of the water level in the cabin. Start the engine and run it at high RPM and watch the water level in the cabin. The vertical movement down tells you how much reduced pressure change there is in the engine room due to the engine sucking the air out.

If you are used to mm of mercury, multiply what you see by 10 (approx). Eg, if you see a 10 mm change in the height of the water level, then that's about 100mm of mercury. An atmosphere of pressure is about 760 mm Hg.

Our engine gets its air from the bilge, so we are also working through these questions and trying to find a solution. In our case, the manometer test showed very little difference, much less than 10 mm. But, the engine room gets hot so we know we need to fix this. Because warm air holds less oxygen than cool air (at the same pressure) this means the engine is being starved of oxygen compared to a cool engine room. Not good.

Also, our battery box is in the engine room - another bad idea we are working on changing.

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Old 27-11-2016, 02:45   #26
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Re: Engine room ventilation

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Originally Posted by Toaster View Post
If you are used to mm of mercury, multiply what you see by 10 (approx). Eg, if you see a 10 mm change in the height of the water level, then that's about 100mm of mercury. An atmosphere of pressure is about 760 mm Hg.
Quite the opposite, 10mm of water = 1mm of mercury
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Old 27-11-2016, 13:28   #27
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Re: Engine room ventilation

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Quite the opposite, 10mm of water = 1mm of mercury
Haha, yes, for sure!
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Old 22-12-2016, 10:03   #28
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Re: Engine room ventilation

Trying to revamp this thread.

My engine-room is pretty close around a 'massive' TAMD-31LA 3lt. 130HP engine
Air intake is mainly from bilge level, stern side.
I measure 62℃ on TOP of engine, say 140℉. Is it too much?

There are two clam vents in the cockpit, are these for intake, or for de-heating? (Being on top of the engine room).
I can measure depression, but really what should be of concern to me?
AIR INTAKE proportionate to engine needs?
Or..
TEMP control, mainly AFTER shut down?

Issue is.. l was thinking about sound insulation of bilges too, since much of the noise/tremble comes through the floor/bilge level... and engine room has got double insulation now.


The generator, being encased, raises concerns on both sides. There is a circular porthole for oil check, that I will cover with a always ON 12V PC fan
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Old 22-12-2016, 10:33   #29
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Re: Engine room ventilation

Quote:
Originally Posted by TheThunderbird View Post
Trying to revamp this thread.

My engine-room is pretty close around a 'massive' TAMD-31LA 3lt. 130HP engine
Air intake is mainly from bilge level, stern side.
I measure 62℃ on TOP of engine, say 140℉. Is it too much?

There are two clam vents in the cockpit, are these for intake, or for de-heating? (Being on top of the engine room).
I can measure depression, but really what should be of concern to me?
AIR INTAKE proportionate to engine needs?
Or..
TEMP control, mainly AFTER shut down?

Issue is.. l was thinking about sound insulation of bilges too, since much of the noise/tremble comes through the floor/bilge level... and engine room has got double insulation now.


The generator, being encased, raises concerns on both sides. There is a circular porthole for oil check, that I will cover with a always ON 12V PC fan
I don't think heat is an issue at all. Ventilation is though, for engine intake requirements. My guess is the engine will suck air thru a vent faster than a PC fan can blow, so not sure about using that, it may slow down the flow.
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Old 22-12-2016, 14:12   #30
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Re: Engine room ventilation

Fan would replace an otherwise closed porthole. It is for genny, a small 1lt. KUBOTA engine.

However, it doesnt improve intake from OUTSIDE the engine room area.

I must check those clammed vents in cockpit, definitely
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