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Blower for engine

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DJgun View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote DJgun Quote  Post ReplyReply Direct Link To This Post Posted: 18 October 2023 at 00:35
Originally posted by Wild Wild wrote:

We still have the Hanse original ( 2010 and +2500 h) Jabsco 35400 100mm/12V
Running continuously and have a delay relay of a few minutes after switch off the engine ignition.
Not one problem so far.

Hi Wild,
The Jabsco 35400 is a centrifugal blower which I believe is the best option in this application. The manufacturer lists the maximum motor life as 1000 hours, so you have been very lucky if it is running already for 2500 hours. Nominally it is designed for intermittent duty.

Cheers, DJ
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Wild Quote  Post ReplyReply Direct Link To This Post Posted: 18 October 2023 at 07:26
Originally posted by DJgun DJgun wrote:

Hi Ratbasher,



When the engine is running it actually sucks in significant amounts of air, including fumes in the engine room. For that reason I don't believe it is necessary to run the blower continuously, but if the blower is continuous rated it gives that option.


I believe it Ďs the best running the blower continues when the engine is running.
The engine compartment in a boat is small and the engine need to suckís a lot of ,and best of all fresh clean air. In a car- our a 🏍 motor thatís not a problem on a sailboat engine compartment the natural fresh air flow is not very good.
On big motoryachts they used big heavy duty blowers with air intake gaps besides the boat.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote DJgun Quote  Post ReplyReply Direct Link To This Post Posted: 04 November 2023 at 11:54
Hi Wild,
The problem with your suggestion is that the fan is sucking air out of the engine  room which is quite small on these boats. The fans are not blowing fresh air into the engine room.

The engine itself is a high flow air pump, which creates but better suction than any small axial air blower/fan, and transfers enough volume too. If the engine is running the electric fan proves nothing but a lower pressure in the engine room, and it is fighting the engine for air supply.

It could be that the engine running will increase rhe pressure drop across the electric fan enough to overload it electrically.


Edited by DJgun - 06 November 2023 at 01:08
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Wild Quote  Post ReplyReply Direct Link To This Post Posted: 04 November 2023 at 15:29
Hello DJgun
Thereís no blower in the fresh air intake 100mm on the bottom of the engine compartment.
The Jabsco blower with 100 mm suction tube is at the top of the engine compartment.
So no obstruction for the engine air intake only continues fresh and cold air flow around the engine.IMO a good ventilation.
After a closer look we have the Jabsco 35770-0092 heavy duty-continues running instead the 35440
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Post Options Post Options   Thanks (0) Thanks(0)   Quote DJgun Quote  Post ReplyReply Direct Link To This Post Posted: 04 November 2023 at 23:05
Hi Wild,
That is an excellent blower you have, continuous rated. Interesting that you have 4" ducting. On my 400 ( l2007 build) I have only 3" duct, and only an extraction duct, no fresh air duct. There are various openings between engine room and the lazarette area which is where the engine draws it's air, as well as through the extraction duct in the reverse direction if the fan isn't running.

It looks like you have a generator tucked in the engine room too. Is that to power the 11 amp draw from the fan? 😉 Fisher-Panda?

I won't run my fan continuously as I see no need to it for the reasons I stated,  but if you want to run yours continuously that's fine too. I have seen the odd yacht which the OEM  has configured one fan blowing into the engine room, and another extracting air from it. I can't remember if they ran continuously or not.


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DJ
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Post Options Post Options   Thanks (0) Thanks(0)   Quote alidal Quote  Post ReplyReply Direct Link To This Post Posted: 05 November 2023 at 08:28
On my H400 from 2010 there is no fan and it works too...

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Post Options Post Options   Thanks (0) Thanks(0)   Quote sgrhma2 Quote  Post ReplyReply Direct Link To This Post Posted: 05 November 2023 at 16:30
Iím the same my 2005 370 has no blower fan. The engine itself is an extremely high capacity air pump in itself and will shift vastly more air than all the blowers mentioned. 
Blowers were originally fitted to boats to clear fumes or dangerous vapours from gas appliances and petrol engines (which use to be all carburettor fuelled and off gassed at shut down) and the blower was run for a while to clear the bilges of potential explosive gases before starting the engine. This was done to minimise the risk of fire or explosion when activating the starter and the associated electrical spark risk. With the move away from inboard Petrol engines blowers were still fitted and then in general became a regulatory requirement. 
While not having one on my boat, I have considered fitting one as I still have gas onboard for cooking and a small amount of petrol. Having said that I feel it is more important to properly maintain the gas system and store the petrol correctly than go to the grief of fitting a blower. However if you already have a blower maintain it properly, but donít get hung up if it stops working, add it to the end of season maintenance list, but at all times look after your gas system and how you store any petrol onboard.

Simon 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote S&J Quote  Post ReplyReply Direct Link To This Post Posted: 06 November 2023 at 00:02
I think that the main purpose of the blower is to extract hot air and fumes and vent these at the stern rather than simply have them passively vent into the cockpit.  I don't think that it is required to facilitate the engine airflow.
On a previous Beneteau the engine compartment didn't have a blower and we got a distinct diesel smell from the vents either side of the companionway.  Installing a small blower resolved this.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote DJgun Quote  Post ReplyReply Direct Link To This Post Posted: 06 November 2023 at 00:52
The posts from various owners with different production year boats is very interesting.
From the various contributions  it appears that Hanse didn't even fit engine room fans in 2005, 2006, then fitted a fan in 2007/2008 but didn't include the fan in wiring schematics, and then a year or two after they stopped fitting them again.   In 2007 they used 3 inch fan and a single duct, but at some later stage it seems from posts they used 4 inch and two ducts. Clearly Hanse had trouble coming to a firm conclusion about what was needed.

I agree with previous two posts on a couple of points.
Firstly the fan should be run before starting the engine  to remove any combustible fumes which could ignite from starter motor/solenoid operation. Just a safety precaution.
Secondly running the fan immediately after stopping the engine to remove any hot air, diesel fumes etc. A matter of comfort.
During running the engine itself does create a slight under-pressure in the engine room as it is an effective pump,  which should prevent fumes and smells escaping into main cabin area. The fan is thus not necessary while the engine is running.  

While the engine is drawing in significant amounts of air, it is not as much as some might think. The 3JH4E Yanmar is just 1.6 litre, so at 2400 rpm it is only drawing 1920 litres of air per minute (67 cfm). A 3 inch Jabsco 36740 is nominally 150 cfm for comparison. As the engine room is less than 2 cubic metres the engine will effectively draw in all the engine room air in under 30 seconds  when running. The Jabsco will nominally do it in less than15 seconds.
My own personal opinion (as a retired engineer) is that a fan is a good idea, but that it only needs to run before starting and after stopping the engine. If you want to fit one then either axial flow or centrifugal fans will work, but a centrifugal offers superior characteristics for this application.

Cheers
DJ


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Post Options Post Options   Thanks (0) Thanks(0)   Quote Wild Quote  Post ReplyReply Direct Link To This Post Posted: 06 November 2023 at 10:35
DJ gun
Our 2010 Engine is Yanmar 4JH4 HTE turbocharged 2 litre
Maybe thatís the reason ??

Wild and Wet
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