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post #11 of 25 Old 06-27-2019
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Re: Engine Ventilation Fan always on

Most `1980's-'90's era Beneteaus were/are equipped with an exhaust fan mounted on the inside face of the transom with ducting to the upper reaches of the engine compartment to suction hot air out of the space. Most are also fitted with two or so static ducts from the transom to the bottom of the engine compartment to return relatively cooler external air to the compartment which reportedly improves the efficiency of the engine and minimizes the transfer heat to the accommodation. The fans normally only run when the engine ignition circuit is activated. (On our boat, however, I have added a separate power switch to activate the fan with the engine "off" to continue removing hot air for a period while the engine cools after a run.) To date I have not found any of these fans to be particularly "nosy" save in cases where the bearings in the fans are failing

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post #12 of 25 Old 06-27-2019
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Re: Engine Ventilation Fan always on

If the fan is mounted somewhere it’s noisy, perhaps relocate it to the engine compartment. Easy job. Just be sure the flow is the right direction.


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post #13 of 25 Old 06-27-2019
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Re: Engine Ventilation Fan always on

As mentioned above, diesel engines consume a great deal of air when operating. Just to give you an example, one vessel I operated had a Gardner 8LX and several generators in a real engine room. Being built in NZ for trips to Antarctica it had a sealed engine room and needed intake fans for the engine and gensets to run. It also had a waterproof door. When the fans were on and the engines not running, it took my full weight against the door to close and dog it, but when the engine was running, I could close the door with one finger.
Very few if any of us have airtight engine rooms, therefore there is plenty of air is getting in to power our small diesels. No additional fans are required. I believe the reason for engine room exhaust fans is to exhaust heat from the engine space after running or remove smoke, engine exhaust or steam when a problem occurs.
Perhaps the OP on the boat in this thread had an exhaust leak he was too lazy to fix and the running the exhaust fan was his solution. I don't know. So many of us find odd systems on the boats we buy.
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Last edited by capta; 06-27-2019 at 02:02 PM.
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post #14 of 25 Old 06-27-2019
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Re: Engine Ventilation Fan always on

Quote:
Originally Posted by svHyLyte View Post
..... The fans normally only run when the engine ignition circuit is activated. (On our boat, however, I have added a separate power switch to activate the fan with the engine "off" to continue removing hot air for a period while the engine cools after a run.) To date I have not found any of these fans to be particularly "nosy" save in cases where the bearings in the fans are failing

FWIW...
Interesting.... The fan circuit on Shiva is wired to the ignition key switch which has several positions... the first one is OFF, followed by ON...followed by the position which energizes the solenoid and starter and then the switch "springs back" to the on position... because you don't want the starter to keep engaging once the engine is running. Fan and instruments are powered by the ON position. After the diesel is starved to stop the engine... you would normally turn the switch to the OFF position... but you can leave it in the (noisy) ON position to continue ventilation. Fan is a power hog. The engine compartment is not sealed... and there are many paths for combustion air to enter. As Cap writes... the exhaust fan will pull smoke and odors and direct it out.

Mine exhausts thru a grille inside a coaming pocket... warm air for autumn sailing but YUCK in summer.

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post #15 of 25 Old 06-27-2019
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Re: Engine Ventilation Fan always on

If the ignition switch is left in run to allow the fan to cool engine compartment after shut down, ,,good chance the alternator energized too .

Last edited by Capt Len; 06-27-2019 at 01:01 PM.
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post #16 of 25 Old 06-27-2019 Thread Starter
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Re: Engine Ventilation Fan always on

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Originally Posted by SV Siren View Post
My current boat has a fan, for exhaust only. I also have a vent which directs the air pulled by ol' Perky over the alternator, and then it get used by the engine. The fan I have set up on a manual switch to exhaust the engine bay once the engine is shut down to exhaust the fumes and dissipated heat from the engine. That helps quite a bit, to reduce the fumes and heat down below.
That sounds like a great idea. Use the fan for a few minutes AFTER a hard run.

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Re: Engine Ventilation Fan always on

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Originally Posted by SanderO View Post
Interesting.... The fan circuit on Shiva is wired to the ignition key switch which has several positions... the first one is OFF, followed by ON...followed by the position which energizes the solenoid and starter and then the switch "springs back" to the on position... because you don't want the starter to keep engaging once the engine is running. Fan and instruments are powered by the ON position. After the diesel is starved to stop the engine... you would normally turn the switch to the OFF position... but you can leave it in the (noisy) ON position to continue ventilation. Fan is a power hog. The engine compartment is not sealed... and there are many paths for combustion air to enter. As Cap writes... the exhaust fan will pull smoke and odors and direct it out.

Mine exhausts thru a grille inside a coaming pocket... warm air for autumn sailing but YUCK in summer.
That sounds like a good idea except for the 1,000 db alarm that sounds when the ignition switch is on and the engine is not running.

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post #18 of 25 Old 06-27-2019 Thread Starter
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Re: Engine Ventilation Fan always on

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Originally Posted by capta View Post
Perhaps the OP on the boat in this thread had an exhaust leak he was too lazy to fix and the running the exhaust fan was his solution. I don't know. So many of us find odd systems on the boats we buy.
You have an evil mind. I like it.
I would never have thought of that but it sure sounds plausible.
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Re: Engine Ventilation Fan always on

So the question is does anyone know if the Bene's were wired this way from the factory?

This boat sunk and they spend 70+ k to refurb the inside.

Maybe the electrition was used to power boats.

I swear I can hardly tell if the engine is off or on with the fan running.

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post #20 of 25 Old 06-27-2019
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Re: Engine Ventilation Fan always on

Have owned three diesel powered boats without an engine fan. Have run those engines continuously for as long as 72 hours including one 24 hour run in the doldrums when it was blazing hot. Never had a problem but then didn't have any exhaust leaks to stink up the boat. No reason not to run an exhaust fan for the engine compartment but it's not necessary with normal air leakage in and out of the compartment. Maybe if you sealed it up tight with virtually no air leaks you'd need an exhaust fan. If you have a fan, no harm in using it but wouldn't waste money and effort installing one or replacing one that died.
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