No Engine Room Ventilation

[Dave_E]

Hi All,
I know last week I asked if you had ventilation in your engine rooms and didn't know if I did for sure. The 36' Taiwanese is on the hard and I've spent many hours down below. I HAVE NO VENTILATION, no fan, no outlet. No wonder I have diesel smell! [emoji35]

I am totally open to suggestions, especially from you Taiwanese owners. Thanks.

Dave

 

[O C Diver]

Added a new ventilation system to my engine room during my refit. It keeps the temperature below 110 degrees, if I remember to turn it on. If you add an exhaust system, remember to increase the fresh air inlet. Engine manufacturers have specific guidelines for fresh air requirements. Don't starve your engine(s).

Ted

 

[Xsbank]

You have to have something or your engine wont run. You dont necessarily need a fan but there must be some air access.

 

[Dave_E]

You have to have something or your engine wont run. You dont necessarily need a fan but there must be some air access.

There is a small opening in the floor to the backside of the refrigerator, but when the refrigerator fan is on, it just draws engine room smell right into the cabin. ?

 

[Martin J]

I did a major upgrade to my engine room , that had a single jabsco exhaust fan in it when I bought the boat. Even having the deck acess door open the E.R. would hit 140F in the Caribbean. I installed two blowers vented right to the engine intakes blowing ambient 85-90F, and 2 high capacity ducted extractors (from surplus sales of Nebraska) venting through the saloon side. These have 6" aluminium ducts strategiclly placed in the E.R. to make sure we pull heat out asap and have a crossflow though the E.R. Now we run 110F the engines run better ingesting cooler /denser air. Plus the 'Biggie" is entering the E.R. under way "one does'nt die with ridicoulous 140F heat"

Of course as soon as we shut down the temp climbs so we tend to leave an extractor on for a while when stopped.

 

[BrianSmith]

I recently spent a couple of days, and several hundred dollars, trying to improve the ER ventilation on our boat. (It's better, but still hotter than I'd like, and the fan is LOUD! Oh, well. Maybe I'll tackle it again sometime.)

But I had something to start with - 4 small "blower fans" bringing outside air into the ER, and a 12" fan sucking the hot air out of the ER, and pushing it through some ducting to the outside. If you don't have anything to start with - you're going to have to find a way to get outside air in, and the ER air out. The blower fans - they seem to go up to 4" diameter - don't move much air - 350 CFM was the best I could find, and that's under ideal conditions. But if you can get 2 or 3 of them in various places around the ER, it adds up.

The exhaust part was the hardest for me. The existing ducting for it was very restrictive, and had 2 90 degree bends. I was able to open that up a bit, and put a shroud around the fan to make sure it was moving air only from one side of the fan (the intake side) to the other - but it's still not ideal. You may have a place you could install 2 - 3 4" blowers to exhaust the air?

One thing that's important is the placement of the cool air intake and the hot air exhaust - the intake should be low in the ER, preferably on the opposite side of the exhaust, which should be at the highest point in the ER. If the intake and the exhaust are both high in the ER, it's very inefficient at getting the hot air out.

Delta T Systems in Riviera Beach, FL has some helpful info on their website. (Delta T Systems Engineered Marine Engine Room Ventilation). I got my 12" fan from them, and that's where I found the highest capacity 4" blower fan - but I couldn't fit it into the space where my exisiting 4" blowers were, so I couldn't upgrade to them.

 

[O C Diver]

Use a 4 " fan to exhaust the engine room. It discharges into a 5" id smooth bore duct. The 5" duct makes a huge difference in frictional line lose over 4".

Ted

 

[psneeld]

Hi All,
I know last week I asked if you had ventilation in your engine rooms and didn't know if I did for sure. The 36' Taiwanese is on the hard and I've spent many hours down below. I HAVE NO VENTILATION, no fan, no outlet. No wonder I have diesel smell! [emoji35]

I am totally open to suggestions, especially from you Taiwanese owners. Thanks.

Dave

What brand and do you have any pictures of the side of your boat?

While some boats have hard to see/locate ventillation, never have seen a boat without it.

Sure a PO could have covered them up, but cant imagine that.

 

[Nomad Willy]

You have ventilation if your engine continues to run. The engine is a good air pump.

That's all I have but I only have 40hp.

 

[Rossland]

Everything you ever wanted to know about engine room ventilation:

http://www.proboat.com/2015/06/venting-the-engineroom/

 

[C lectric]

There is a small opening in the floor to the backside of the refrigerator, but when the refrigerator fan is on, it just draws engine room smell right into the cabin. ?

That's haywire. CLose that vent off. It should not be open to the ER. The fan you are referring to, is it the fan installed as part of the compressor unit?
If so then ideally there should be another fan mounted higher in the fridge enclosure that exhausts the heated air from the fridge to the outside, either the cabin or literally outside or the fridge cooling will be affected. There will need to be a supply vent at the bottom of the fridge cavity also.

Xsbank is right, as are the others. There must be a vent or two somewhere or the engine will not run or run poorly.

Take a good hard look at the hull as often there are louvred vents installed. Sometimes the vents are in the cabin sides somewhere. They may be inadequate, they may be blocked somehow, but they should be there.

Fans definitely can be used to good effect. However I would suggest that the exhausting ability should equal or exceed the supply capacity. If not then the supply may pressurize the ER and force ER odours into the cabin areas. The engine itself is a huge air pump so it will be busy exhausting, it just needs some help aimed mainly at reducing running ER temps.

Do you have a thermometer. Wireless units are available from many places that are battery operated . They run on a couple AA dry cells. The base unit can be installed, velcro, on the dash in sight and the remote unit installed in the ER. Then you will know what the temp. is and that can help guide what you do. I got mine from Radio Shack.

There are many good suggestions in the posts above for how to deal with bettering the venting.

 

[Sealife]

I would also investigate the diesel smell. Engine room ventilation should be for temperature control, not evacuating smells. You may have an underlying problem that needs addressing.

 

[Lepke]

If you don't have a walk in engine room, and there are proper openings for combustion air, the diesels cycle more air in a minute than any blower. Do the math. If you keep fuel leaks under control and the engine clean, you won't have a diesel smell. The fuel is all enclosed. There are no vents like a carburetor or older car gas diaphragm lift pumps.
I have 4 diesels in my engine room and wash them down with soap as needed. Usually dish soap or a strong detergent like Super Clean. I don't have a diesel smell there or anywhere else in the boat. Fuel tank vents are on the open deck. ER is closed off from the rest of the boat. Cable runs, etc., air tight. I have a squirrel cage blower, but only run that after a run to cool things down or when welding, etc. Rags should be kept in a sealed container. Be careful changing fuel filters. I'm not very meticulous, but I have to be with fuel.
If fuel isn't present, there is no smell. If everything looks clean, no leaks, then you have diesel in the insulation, bilge, deck plates and so on. Maybe you need to paint.

 

[Dave_E]

Found it

Hi All,

Thanks for the replies and discussion! The Mrs. and I were leaving the yard today and saw a Defevor 40 with what appeared to be wooden louvered vents along the starboard cat walk. Sure enough we have them too... don't know how we never saw them. The fwd vent is a little "boxed" airway that goes up through the main cabin floor under the helm seat. Then there is one aft just outboard of the deep storage. So, I need to install a fan and some ducting to get it to that cutout in the floor.

As to the diesel smell... the engine room has had it's share of sloppy maintenance over 40 years. Floor boards are rotting away, etc. It's going to be a process for sure. I'm cleaning the remnants of the last ordeal with the loose, spraying #1 injector. Today I replaced the flooring under the house water pump and wash down pump (totally rotted away).

We're going to get there, no hurry, that's part of the journey. Just glad I found what I was hoping was there. Thanks for all your input.

Dave

 

[CaptSteve53]

In very basic terms You should have really speaking a couple of in fans leading to the lower part of the engine room and a couple of out fansfrom the highest point of your engine room,

All hooked up thru a relay to to your ignition system (so you dont forget!)

There's numerous 3" or 4" inline fans available if mounting is an issue

Cheers Steve

 

[psneeld]

Just make sure they are continuous rated fsns if hooked to the ignition.

Many of the smaller inline ones arent.

 

[CaptTPT]

If forced air fans move significantly less air than your engines aspirate at cruising RPM will they have any significant impact on the delta T?

 

[markpierce]

The engines will suck in air if the boat's designer provided air ports, with the exhaust removing the intake. Exhaust fans are a nicety, not a necessity, for a diesel boat, unlike a gasoline boat. Regardless, I've an exhaust fan which used when needing to access the engine compartment shortly after shut-down although that's probably an useless exercise since engine-access is from overhead hatches.

 

[CaptSteve53]

The engines will suck in air if the boat's designer provided air ports, with the exhaust removing the intake. Exhaust fans are a nicety, not a necessity, for a diesel boat, unlike a gasoline boat. Regardless, I've an exhaust fan which used when needing to access the engine compartment shortly after shut-down although that's probably an useless exercise since engine-access is from overhead hatches.

Wow! thats a huge generalization I'm sure , here's what a correct blower system does or consists of in any sized engine room:

An engine room ventilation system is of great importance to the engine life. In many vessels, there is enough air for engines to burn their fuel, but not enough to cool the engine room as well. Since warm air doesn't hold as much oxygen, engines end up with less power, and less efficiency. Engines will need to burn more fuel in order to achieve the same power level.

1) Keep equipment in the engine room clean and in better working order
2) Increase the engine life
3) Reduce the required maintenance
4) Engine room heat doesn't just affect engines, it also damages other equipment such as generators, cooling, and electrical systems

And a couple of final thoughts for the day

A) Engine room ventilation systems consist of both intake fans, which insert combustion air and cooling air, and exhaust fans, which pull out cooling air only. In case the temperature in the engine room rises, the exhaust fans start to pull out cooling air. Consequently, the resulting depression in the engine room ramps up the intake fans.

B) The greater need for proper ventilation can be attributed to the advancement in turbocharged diesels as well. With more air needed to allow the engine to achieve a proper combustion cycle, the design and implementation of the properly sized fans and vents are increasingly more critical. This is especially true on refits when a new set of higher-horsepower engines is going into a tight space. The engines will most likely choke if you wait until after the installation to consider the air requirements of the new power.

So you see it's a little more complicated if you value you engine and engine room ancillary equipment

Cheers Steve(MIIMS-Lloyd's Maritime) NZ Chief Engineer 1

 

[markpierce]

Phew on turbocharged engines. I trawler needs no more power than to reach hull speed. Eighty horsepower is sufficient for 40-foot plus. If engine-compartment inlets are insufficient to supply air to the engine, that boat is wrong.

Forced air intake could blow hot engine-room air into living quarters.

 

[CaptSteve53]

Phew on turbocharged engines. I trawler needs no more power than to reach hull speed. Eighty horsepower is sufficient for 40-foot plus. If engine-compartment inlets are insufficient to supply air to the engine, that boat is wrong.

Forced air intake could blow hot engine-room air into living quarters.

As above my last post it's not about what the engine requires it's about all the other ancillary requirements (did you read the post?)as listed in 1,2,3

Again the correct system uses intake and EXHAUST fans so no air is ever forced into living spaces (quite the opposite actually)

Newer manufacturers recognize this importance where older vessels and there builders did not place enough emphasis on these issues, Engine rooms with out a correctly installed ventilation systems tend to have more issues with ancillary equipment as a part of being to hot (common sense)



Cheers Steve

 

[Ski in NC]

Engine room blowers for these types of boats are simply not needed. I have designed propulsion installs from around 27hp up to around 2800hp and also troubleshot boats where it was claimed the ventilation system was inadequate. In all cases it was a non-issue regarding air inlet temperature to turbo compressor suction, which is where it matters.

The amount of air getting drawn in on the larger engines is tremendous, and actually suction temperature drops quickly to near ambient once up to power. You would need like 5hp fans to move enough air to make any difference, and it is simply not needed.

At low power engine room temps do climb, but at low power settings the engine is not affected by the higher temps. Ancillary equipment (pumps, alternators, generators) generally are designed for these temps and when measured in worst case temps, they were below mfr limits.

The one situation where engine room temps often become an issue is running the generator after a main engine hot shutdown. The gen end is air cooled and the gen engine simply does not use enough air to draw in much cool air. In those cases we did see some excessive temps and then forced ventilation did matter. But it could be a relatively small fan as the added heat rate was low.

On small non turbo engines running trawler service, those are simply not sensitive to elevated intake temps. In that duty cycle, there is so much excess air in the process that the density change from going from say 80F to 120F does not matter much. Note that the density change must be considered in absolute terms (deg Rankine) so the density difference is 80+460/120+460 or 540/580=0.93 or a loss of 7% of available oxygen. If no soot out the tailpipe, not a problem.

 

[CaptSteve53]

My final word (I Promise) you would be surprised at how may insurance claims i attend for engine room equipment failures and how many are thrown out on THE GROUNDS of not meeting the manufacturers ambient operating temperatures,

I stress again it's not ONLY about the Turbo or not requirement, Engine-room ventilation falls into two categories, those required for cooling the space, and those needed for combustion. The air used to cool the compartment improves not only the combustion efficiency, but also the longevity and efficiency of gear in this space, including engines, generators, compressors, and electrical and electronic components (and also makes it a more comfortable place to work). Where generators are concerned, while the engine portion is typically liquid cooled, the electrical generation end relies on air from the engine-room for its cooling (a small number of generators rely on liquid cooled stators). When engine-room temperature is excessive, generator manufacturers will often lower the unit’s rated output.

Additionally, heat takes a toll on “soft goods” such as generator couplings, belts, motor mounts,torsional vibration dampers, transmission damper plates, hoses, insulation, voltage regulators, and other electrical and electronic components, as well as batteries.

As a general rule of thumb, (these apply to wet exhaust engines) to determine the necessary air flow rate, in cubic feet per minute, use this formula (2.75 x hp) – 90. Having said that, it’s wise to defer to requirements established by engine manufacturers, or whichever is greater.

Caterpillar’s standard guidelines for forced ventilation call for 2.5 ft3 (.07m3), per horsepower, while one generic rule of thumb for passive combustion air inlet surface area specifies 0.55 in3 (9cm3) per horsepower (including generators). The Cummins guideline for passive vent surface area size uses the following formula, rated engine air intake, specific to each model, in cubic feet per minute, multiplied by 0.272, equals required area in square inches. Failure to follow these formulas is a common violation for new builders, particularly where designs evolve to accommodate larger engines with no changes made to intake size. It’s important to note that the cross section must be measured at its narrowest restriction (and louver area must be subtracted); it’s not unusual to find large louvers that supply air via significantly constricted duct work.

FINAL WORDS

Due to the nature of my position as a (MIIMS) Lloyd's Maritime surveyor -(NZ Chief End 1)specializing in engineering installations/refits, I get to see a host of so called "Professional Installations" that dont meet manufacturers specifications and have spent CONSIDERABLE TIME in courts as an "Expert Witness" facing well known international boat builders out lining there failures and the belief in there systems.

"You can lead a horse to water but you cant make it drink"


Cheers Steve

 

[Martin J]

Steve
Well explained and in total agreement,. When I did my e.r. my 2 x120hp lehmans needed some 240cfm each, so I installed 2x400cfm blowing the outside ambient air at 85-90f at the intakes. (low down in bilges) Performance improved , more power at lower rpm, saving fuel etc. I also put 2x650 cfm extraction fans to achieve neg e.r. pressure. Actually impossible the E.R. main deck door is always open to allow lots of airflow. I got my E.R. temp from the 140f to operating around 110F. Heres a interesting website for engine CFMs http://powertherm.com/PT2/images/PDF/DonaldsonAirFiltration251-258.pdf maybe this will peak some of the other members interests about improving there E.R. efficiency.