Should the engine bay blower be always on?

[rwidman]

Originally Posted by Hudson Force

rwidman's observations here are clear and valid; however, many might not consider the term blowing to be directional. I would think a "blower" could move air in or out of an engine room. The blower that moves hot air out of my diesel engine room does not create a partial vacuum. I have places where air can enter by means of an open opposing vent as well as unsealed doors and lockers leading from my forward cabin, aft cabin and center cockpit.

I would elect to have the air from my engine room expelled with cooler, fresh air entering. Blowing air into my engine room would increase the heat, odors and potential carbon-monoxide entering my cabins.
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Your point of possibly blowing fumes into the cabin by pressurizing the engine compartment is well taken. On the other hand, you don't want the engine compartment to be at less than ambient pressure. The trick here is to have enough openings to allow plenty of fresh air in to compensate for any exhaust fan.

As I posted, my (diesel) boat has no fan so I suppose the designers figured it all out before building the boats.

We haven't answered the OP's question but he never said if he had a gasoline or diesel powered boat and if he has a switch for the blower. Or if it's possible that a PO chaged things from the factory setup.

[a64pilot]

Originally Posted by rwidman

It's not terribly difficult to tap into the engine's cooling system and run the coolant through a heater in the cabin, similar to how a car heater works. I believe you can buy these ready to install.

You can buy a bus or truck heater that is a complete assembly with fan and everything, then use Y valves to run the hot water that normally goes through your water heater and now run it through your bus heater. It is a surprising amount of heat, more than you get from your car heater, but exactly the same principle. Switch the valves back for hot water of course

Here is one, $160 and 26,000 BTU, an average airconditioner / heat pump is only 16,000 BTU for example, so this ought to be able to make a sauna out of a small boat if you desire, of course just like your car heater turn the fan on low when it gets hot, or off.
https://www.summitracing.com/parts/m...FdU6gQod3NoG0A

There is just enough room on my boat under the companionway steps for one, but I do not think I will fit one, my plan is to stay in warm weather

[GordMay]

See also ➥ http://www.cruisersforum.com/forums/...-it-37561.html

And ➥ http://www.cruisersforum.com/forums/...wer-42656.html

And ➥http://www.cruisersforum.com/forums/...ort-23264.html

And ➥ http://www.cruisersforum.com/forums/...ion-85829.html

[rwidman]

Originally Posted by a64pilot

........... my plan is to stay in warm weather

Mine too although once or twice I have gotten out my electric space heater and run it off the inverter while underway.

[a64pilot]

Originally Posted by rwidman

Mine too although once or twice I have gotten out my electric space heater and run it off the inverter while underway.

I'll admit to cranking the generator and running the airconditioner in heat mode myself.
I discovered in Bosnia and had it re-affirmed in Korea, I am allergic to cold

[svHyLyte]

Originally Posted by rwidman

...

We haven't answered the OP's question but he never said if he had a gasoline or diesel powered boat and if he has a switch for the blower. Or if it's possible that a PO chaged things from the factory setup.

The Jenneau 409 is typically fitted with a 40hp Yanmar. The boat is fitted with an evacuation blower from the factory that is activated when the ignition is turned on. If, as the OP indicated, the blower is rated at 150CFM, that would provide, roughly, 2.3 air changes per minute to the 409's engine compartment.

FWIW...

[captain58sailin]

I use my engine room blower to exhaust excessive heat on one side, and to bring in cooler air from outside on the other. All the tugboats and ships that I have been on had massive blowers, one side sucks and the other blows, it keeps the engine compartment cooler and provides cooler air for the engines to burn.

[svHyLyte]

Originally Posted by a64pilot

I'll admit to cranking the generator and running the airconditioner in heat mode myself. I discovered in Bosnia and had it re-affirmed in Korea, I am allergic to cold

FWIW we have a Heatercraft Heater plumbed into our cooling water">engine cooling water circuit with a Y-Valve that can be opened during colder months and have found it does an excellent job of keeping the boat warm during the cold months when we're aboard, even for some while when the engine is not running from the latent heat in the coolant after he engine's been shut down. A little costly, perhaps, but well worth it.

[jag3man]

The blower (if properly installed) will suck fumes from the lowest parts of the bilge in the engine compartment. That's why it shows up in your owners manual. Some say open the hatch or run the blower for five minutes prior to starting. This is for gas engines and to prevent explosion. For diesels I suppose it could supply fresh air but a diesel of any size consumes hundreds of cfms while running and will draw in much more air than the fan.

[GordMay]

Greetings and welcome aboard the CF, jag3man.

[jag3man]

Originally Posted by GordMay

Greetings and welcome aboard the CF, jag3man.

Thanks Gord

[kas_1611]

When I changed out the diode splitter on our Alternator charge system for a zero volt drop 3 way splitter I discovered that my engine room extractor fan wouldn't work properly. It would come on as soon as the ignition was live rather than when the Alternator was running.

So I ended up disconnecting it which had the side effect of making the helm area much quieter with the engine running, especially when trying to communicate during mooring or anchoring when one of us is at the bow and the other on the helm.

However, I was slightly concerned that there could be temperature related issues so I investigated what the temperature difference was in the engine room with and without the fan running. I discovered that even after an entire day on the engine the actual temperature variation was 5ºC. So there actually was very little engine room cooling at all with the fan running. I checked the temperature rating of some of the electrical components and found they were rated to 70ºC so well above the 45ºC I saw without the fan running. So nothing to be concerned about there.

As my engine bay is open right back into the transom there is also no way this tiny 4" fan could create a negative pressure nor would it help the engine breathe. I'm pretty sure the engine can suck more than enough air naturally so can't see how the fan would help. I'm even swapped my paper filter for a K&N filter (but that's because I baulked at the £80 for a replacement paper unit).

However, as we had the fan and all the ducting in place I figured it would be good to use it when the engine was running for more than an hour. I rigged it up to a spare switch on my instrument panel so we can manually turn it on or off as and when we need it. Especially off when anchoring or coming in to harbour when we need to communicate clearly.

That's my take on it

Keiron

[S/V Alchemy]

Originally Posted by Terra Nova

Run it whenever the engine is running and for awhile after engine is shut off.

This is the most straightforward answer. You could unnecessarily complicate matters with a timer or an oxygen sensor, I suppose!

[Elie]

Originally Posted by a64pilot

Some boats like mine use the blower to exhaust excess heat, if you blower inlet is at the top of the engine compt, that is what it is for, the ones to eliminate fumes of course draw from the lowest point in the bilge.
Blowers are real cheap, I run mine as the manufacturer intended, lower engine room temps have to be a good thing

I agree completly on this idea. In fact too much heat in the small engine space, may create problems like overheating of alternator(its murder!). But, powerfull fans are noisy. I'm lookin for some sort of thermostatic switch that would start the fan only when temperature reach a certain point. But wher to find this type of thermostatic fan?...

[jakkum]

A 4 ltr engine, 4 stroke, moves 4 ltr of air, every 2 revs. So running at 2000 rpm it moves 4000 ltr of air every minute.
What does a blower move?