Any benefit to adding ER ventilation fan?

[Spinner]

Hello, the engine on my 42 Nordic Tug is a 450 HP Cummins. The engine room has vents but it still gets pretty hot down there even here in the Pacific NW.

I heard somewhere that adding a ventilation fan(s) to the ER will improve engine performance. Has anyone heard this, and is it true?

 

[Fish Isla]

Its a good way to fill the Engine room with salt air and lots of corrosion.

 

[O C Diver]

Hello, the engine on my 42 Nordic Tug is a 450 HP Cummins. The engine room has vents but it still gets pretty hot down there even here in the Pacific NW.

I heard somewhere that adding a ventilation fan(s) to the ER will improve engine performance. Has anyone heard this, and is it true?

It's probably relative to the normal engine room operating temperature. Cooler air and fuel temperatures are more efficient, but I'm not sure you will see a measurable difference.

My engine room with a 2 GPH fuel burn, can reach 130 degrees ( measured near the ceiling) on the hottest days without the 220 CFM exhaust blower on. With the blower on it stays below 110 degrees. This is actually misleading as the blower I installed is in the stern up against the ceiling and the intake air comes under a bulkhead in the hollow keel. I suspect the room is quite a bit cooler than the ceiling with the blower on.

If you choose to add an exhaust blower, remember that you may have to increase air intakes to the engine room so as not to starve the engine. Most engine manufacturers have specifications for free air intake requirements measured in square inches or centimeters.

Ted

 

[Comodave]

Delta-T does a lot of engine room ventilation. They can probably recommend what to do, but they are not cheap.

 

[danderer]

I have both intake and exhaust fans; I find they lower the ER temp at the ceiling about 10 degrees.

 

[tiltrider1]

Sue, as long as your boat moves forward it is self venting. Engine room blowers will help cool down the engine room after a day of motoring were you end up on the hook in a sheltered cove. You will not see any meaningful performance increase because you turn ona blower in your engine room.

 

[High Wire]

So doing the math… An 8 liter diesel at 2000 rpm uses 8 liters of air every 2 revolutions or 8000 liters per minute. Convert that to cubic feet per minute and that is about 280 cubic feet per minute to feed the engine. A 200 CFM fan at stated capacity is close to having a second engine. Pretty significant if you can draw from up high and needs to be considered in sizing the air inlets.

 

[Simi 60]

We have 24v Craig Davies fans X 2 sucking air out and venting it out of rooftop funnel rear

ER ventilation is via 6 X 4 inch stand up pipes on foredeck in front of cabin an a vented locker.


Air intake for engine is a pipe coming from funnel fwd, down to a box and end of pipe has an air filter on it. Pipe from box into engine.

Never seen ER warmer than 37c / 98.6f
But, engine/turbo does not work hard either.

 

[Lepke]

Another reason for an engineroom vent is to cool down the ER after shutdown. If you have keel coolers, an auxiliary pump can circulate coolant and cool down the ER that way, too.

 

[BruceK]

Yes. The few times I forgot switching on the ventilation, the ER was way hotter than usual.

 

[Arc]

High wire, your math is a bit off if the engine is turbo’d

 

[jleonard]

When I did my repower, the Cummins spec was 30 degrees F above ambient as a maximum. The Cummins tech measured the temperature near the engine air filter.

 

[Portage_Bay]

If starving the engines for air is a concern the blowers can be set up to push air in rather than pull air out.

 

[Unclematt]

I have both an engine room exhaust fan and one in the lazerette for the Genset. They do a good job of cooling the areas down. The intake for the engine room is 18 x 12. I also forget to turn it on at times.

 

[rslifkin]

If starving the engines for air is a concern the blowers can be set up to push air in rather than pull air out.

Even on a diesel boat where there's no rule against this, it's a terrible idea in my opinion. At low engine loads you may end up pressurizing the engine room slightly. Which means you'll be forcing heat, smells, etc. out into the rest of the boat through any little gaps.

 

[Portage_Bay]

Even on a diesel boat where there's no rule against this, it's a terrible idea in my opinion. At low engine loads you may end up pressurizing the engine room slightly. Which means you'll be forcing heat, smells, etc. out into the rest of the boat through any little gaps.

I understand your point. It's a balancing act. The exhaust vents have to be big enough to not prssurize the engine room. I ran a boat for many years set up that way. No problems at all.

 

[slowgoesit]

Our engine room has inlet and outlet fans. Running in PNW, we rarely see ER temps > 90 degrees F. Our engine is a medium speed engine, and draws a LOT of combustion air.

Where we see the major advantage is not while running, but as stated previously, after shutdown if we wish to cool down the ER to the outside, rather than having the heat soak into the rest of the boat. Of course, in cooler WX, we just open the ER door after shutdown and heat the boat for the first couple of hours until the ER cools off!

 

[mvweebles]

Somewhere on an archived hard-drive I have a picture of laundry hanging in the engine room of a N57 I was delivering from Dana Point to Ft Lauderdale. The big Delta fans did an amazing job of keeping that ER relatively cool, even in the tropical heat of Panama. Honestly, I cannot imagine an ER without an exhaust fan. Bigger the better.

Peter

 

[GoneDiving]

Be mindful that the location of inlets and outlets have a dramatic effect on the exchange and cooling of the airspace. Mine currently has a forced inlet only about a foot away from the exhaust and both are at ceiling height so there is very little exchange of air. Ideally, fresh air would enter low at one end and exhaust high on the other.

 

[SoWhat]

Not a thermodynamics expert but I suspect fans directed at engine hot spots such as heater core or exhaust manifold would distribute thermal loads but trying to lower the temperature of the whole engine room would require appropriately sized ducting.

 

[High Wire]

High wire, your math is a bit off if the engine is turbo’d

Agree

 

[Spinner]

Yes, the engine has turbo ( Cummins 6CTBA)

 

[Leo Reise]

We had a Jabsco ER blower, the $150 ones normally used. We used it while running to lower the temperature in the ER as our ice box floor was over the ER. We found out the the blower on board estimated life span was 500 hrs. and for intermittent use only. That discovery was in the middle of a 3-week cruise.
We replaced the blower with another Jabsco meant for constant use, estimated lifespan of 5000 hrs. For us, that would be roughly 30,000 nm. BTW - it was not $150 - more like triple. It is mounted on the exhaust side. About 400 CFM. As stated, - it does drop the temperature in the ER, 10 to 15 degrees F.

 

[O C Diver]

So I use one of these Yellowtail exhaust blowers. They routinely last 1,000 hours and cost <$35. I keep a spare on the boat and consider them consumables.

https://www.defender.com/product.jsp?id=4009717

Ted

 

[markpierce]

If starving the engines for air is a concern the blowers can be set up to push air in rather than pull air out.

And possibly to push hot-engine air into living quarters.

 

[Portage_Bay]

And possibly to push hot-engine air into living quarters.

See my post #16

 

[Xlantic]

If starving the engines for air is a concern the blowers can be set up to push air in rather than pull air out.

One issue I see with this approach is that, as mentioned, pressurising the ER could push hot air, smells and even some carbon monoxide into the living quarters.

But if the fans are not powerful enough to pressurise the ER it means they are not pushing in any more air than the engines suck in by themselves so no net benefit when the engines are running.

 

[Portage_Bay]

One issue I see with this approach is that, as mentioned, pressurising the ER could push hot air, smells and even some carbon monoxide into the living quarters.

But if the fans are not powerful enough to pressurise the ER it means they are not pushing in any more air than the engines suck in by themselves so no net benefit when the engines are running.

If designed properly with large enough exhaust ports there will be no issues. As I said up thread I ran a boat for many years set up that way with no problems.

The fans do not need to pressurize the engine room to be effective. They need to move a lot of air to be effective. If the engines get enough air for combustion with the fans off then additional air provided by the running the fans will displace hot air. It works very well.

My suggestion to blow air in was in response to a poster concerned about starving the engines if hot air is sucked out. I doubt most of us have boats with tight enough engine rooms coupled with powerful enough fans to starve the engines for air. Nor are we running our engines hard enough for the temperature of the intake air to make a measurable difference in efficiency. What cooling the engine room does is make everything else in there run better and last longer. It also makes the boat more comfortable during summer cruising which is when most recreational boaters do most of their cruising,

 

[HTurner]

I have two dorade boxes that were mounted atop my pilothouse in a refit going back to 1988. 4" hose leads down to the engine compartment. One dorade feeds air near the engine intake the other dorade exhausts air on the far side. Exhaust side has a 4" inline blower. Helps the boat smell fresh as the dorades keep the bilge dry.