bilge blower question

Gunni

Gunni

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Mar 16, 2010
5,937
Beneteau 411 Oceanis Annapolis
My bilge blower died and I had a new one installed. It is pulling air in from the transom dorade and blowing air into the engine compartment. That seems wrong. There are two passive dorade vents at the companionway. Seems like they should be intakes to a negative pressure engine bay. Wondering how other early 2000's Beneteaus are set up.
 
P

Philip_Oceanis 361

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Nov 23, 2009
437
Beneteau Oceanis 361 Clipper --
My Beneteau 361 has two "holes" at the transom, port to the opening to the cockpit, where two flexible hoses are connected to take fresh air into the engine compartment. There is another "hole" at the transom, starboard of the opening to the cockpit, at which a plastimo bildge blower is connected (and another flexible hose) that extracts hot air from the engine compartment.
 
Gunni

Gunni

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Mar 16, 2010
5,937
Beneteau 411 Oceanis Annapolis
Ron; I need that mechanic, he fits into small places!
 
DougM

DougM

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Jul 24, 2005
2,242
Beneteau 323 Manistee, MI
My 323 has intake and exhaust "dryer vents" side by side through the transom.
One is intake air, other is exhaust. Blower is on the exhaust side venting the hot air out.
Either your blower is installed backward or wired backward.
 
B

Barnacle Bill

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Jun 9, 2008
1,771
- -- -Bayfield
If the wires are backwards, in other words, if the negative wire is hooked up to the positive wire and the positive wire is hooked up to the negative wire the blower motor will run in reverse. I'd check that first.
 
Gunni

Gunni

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Mar 16, 2010
5,937
Beneteau 411 Oceanis Annapolis
If the blower is wired up backwards my concern would be that circuit protection is messed up.
 
Ron20324

Ron20324

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Jan 22, 2008
8,050
Beneteau 323 Annapolis MD
Doug, my B323 has two intake vents, one on either side of the companionway. One exhaust on the stern. Changes from year to year apparently.
 
jviss

jviss

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Feb 5, 2004
6,745
Tartan 3800 20 Westport, MA
One generally wants to blow cool air into the engine space, and have the air exhaust through another vent. If there's only one air passage and you are either blowing or sucking air, you are not ventilating the engine compartment. You need an in, and an out, and typically, if you're heating up the air, the out need be bigger than the in.

The reason you blow is that you don't want to potentially suck combustible vapors into the electrical motor.
 
Ron20324

Ron20324

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Jan 22, 2008
8,050
Beneteau 323 Annapolis MD
jviss said:
... The reason you blow is that you don't want to potentially suck combustible vapors into the electrical motor.
Click to expand
The reason you DON"T want to blow is that you'd pressurize the engine room to a degree, and the fumes would be blown out every little crack and hole into the living areas.
 
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jviss

jviss

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Feb 5, 2004
6,745
Tartan 3800 20 Westport, MA
Ron20324 said:
The reason you DON"T want to blow is that you'd pressurize the engine room to a degree, and the fumes would be blown out every little crack and hole into the living areas.
Click to expand
That's a good point.
 
BigEasy

BigEasy

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Jun 21, 2004
2,533
Beneteau 343 Slidell, LA
My 343 has two small vents adjacent to the companionway and one large vent that terminates under a cowling mounted on the stern.; however, no blower. That's on the project list to install an inline blower in the large ventilation hose that will suck hot air out of the engine room and vent it out the stern cowling. The two vents adjacent to the companionway should be adequate to supply fresh air into the engine compartment.
 
Ron20324

Ron20324

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Jan 22, 2008
8,050
Beneteau 323 Annapolis MD
BigEasy said:
My 343...however, no blower. ....
Click to expand
NO blower? IIRC, that's like a requirement? Maybe it just does not/never did work? I'd look for it, if you have not already, behind the lazz, toward the vent-out cowling.
 
BigEasy

BigEasy

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Jun 21, 2004
2,533
Beneteau 343 Slidell, LA
Ron,
I previously traced the vent hoses. No blower present. The 343 that I chartered many times ,before purchasing mine, didn't have a blower either. Weird??
 
DougM

DougM

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Jul 24, 2005
2,242
Beneteau 323 Manistee, MI
Hey Ron,
my 323 has the vents on both sides of the companionway, They appear to be purely decorative/dead end.
I thought they were actually night lights for the companionway that never worked when I first got the boat. I never cared if they were and didn't work.
 
Davidasailor26

Davidasailor26

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May 17, 2004
5,071
Beneteau Oceanis 37 Havre de Grace
Ron20324 said:
NO blower? IIRC, that's like a requirement? Maybe it just does not/never did work? I'd look for it, if you have not already, behind the lazz, toward the vent-out cowling.
Click to expand
I believe a blower is only a requirement for gas engines. I think Beneteau just uses them to keep the engine area cool; fumes aren't as much of an issue. That's why most of our blowers just come on when the ignition is on rather than needing to be run for a few minutes before starting.
 
Ron20324

Ron20324

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Jan 22, 2008
8,050
Beneteau 323 Annapolis MD
DougM said:
... They appear to be purely decorative/dead end....
Click to expand
I never took the vent covers off, but I always thought the air goes down the hollow between the cockpit mold and the head wall? Maybe not so? That is the only way I see fresh air getting into the engine room.
 
Gunni

Gunni

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Mar 16, 2010
5,937
Beneteau 411 Oceanis Annapolis
The blower creates negative pressure in the enclosed engine bay which is relieved by the intakes. You should have flex-ducting from all dorades into the engine bay. Diesels run best and cleanest with plenty of fresh air, and the boat remains fume-free if those fumes are being expelled out the transom.
 
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