Fan in the engine room

[JulianGullsway]

Hi All, I'am looking for some advice, our lovely 4108 has a tendency to on occasions cut out due to air intake in the fuel and I think its down to a lack of ventilation in the engine room, I've had Gullsway for a number of years and know the engine very well and the fuel is clean the tank is inspected and cleaned every year if not more (we have had fuel issues in the past) My point is I was thinking of putting in a fan sucking cooler air from the outside to help the engine... Can you see any problems with me doing this or are we OK just to get a bilge blower with some ducting and fitting it!!!

Thank You in advance

Julian

[ctl411]

We have one that "pulls" air out of the engine room and a intake vent to let air in. Nice to pull the heat out while running and after shutdown.

[UNCIVILIZED]

I'm not sure that I understand your thinking on how air is making it's way into the fuel system. Might you be kind enough to expound on this please.

As to helping out the engine via adding ventilation, I'm sure that the engine will thank you for it, whichever method you choose. Though you might first take some temperature readings in the engine compartment when it's running to see if there's excessive heat in there.

How well sealed is the compartment, & if it's fairly tight when it's closed up, would the extra noise inside of the boat bother you? Or, if you add ventilation, would you be up for incorporating sound insultation into the plumbing for the air intake/exhaust so that things remain relatively quiet? As the general rule of thumb is that if an engine compartment is pretty loose, & you seal it, the volume of sound drops by about 50%.

[dlymn]

We suck air out rather than blow it in. The logic was that blowing might push heat and fumes into the cabin if there was an opening at all. you must have some form of outlet. We do get some back pressure as the in-line fan tries to push air through 3 metres of flexible ducting.

[Hudson Force]

I run an engine room exhaust blower while my engine is running and this is paired with a fair sized vent for air entering. I'm dismissing your "air intake in the fuel" as a misrepresentation of the ventilation starved engine.

If we are speaking of an air ventilation problem, be sure to try running the engine with the doors and covers all open to determine if the engine runs well with open ventilation.

[svHyLyte]

Most engine room/compartments vents that I have seen have ducting to the highest point in the compartment that is connected to a remotely mounted exhaust fan (in our case on the inside face of the transom) and additional ducting that allows cooler/ambient air to be sucked into the lower portion of the compartment. Note, however, that the foregoing has nothing to do with air being sucked into a fuel line which, more likely, is due to a loose fuel line fitting or improperly seated o-ring in a fuel filter assembly.

FWIW...

[roverhi]

Have had two boats without forced air ventilation for the engine space. No problems. There is enough leakage of fresh air into the space on most boats that it is not really necessary for diesel engines. Forced air into/out of the engine spaces may give you a small increase in engine efficiency but probably not enough to justify the expense and hassle of routing the plumbing. If you have a waterproof engine space on your boat, highly unlikely, ventilation would be necessary.

Getting air into the fuel system has nothing to do with ventilating the engine space. If that is happening, you'll have to go through the complete fuel system from the tank to the injectors to find where the engine is sucking air into the system.

[rourkeh]

Not sure how lack of air is your problem.
If you want a real surprise look up the suggested operating temperature for your engine and then take a reading of the engine-room temp after it has been running for a couple of hours.
On almost all sailboats you will find that due to poor design of these spaces you are cooking your engine. The primary cause of premature engine failure is excessive heat. A continuous duty blower will go a long way to solving this problem. Do not buy one of those cheap pos blowers from the marine store it will die a rapid death. Try Delta T Systems or similar. Your engine will live a lot longer.

[dlymn]

Temperature of air in engine room probably won't have a great impact on the engine. I don't think it will cause it to expire. Each cylinder is surrounded by water at about 80 degrees C. The thermostat and the sea water heat exchanger keep it that way. The hotter the cooling water gets, the more cooling water is admitted into the system. It's true that when people discover that their engine has blown up, the engine and the engine room are very hot. That's because there is no coolant in the engine, not because the air is hot. If the engine is working properly, the surrounding air will always be cooler than the engine.

[markpierce]

Originally Posted by ctl411

We have one that "pulls" air out of the engine room and a intake vent to let air in. Nice to pull the heat out while running and after shutdown.

Same here except don't see the need for continuous powered air exhaust. The engine sucks in air which is ultimately exhausted to the exterior.

Perhaps the OP has a clogged engine air filter.

[Suijin]

The engine room on a Valiant is essentially completely sealed. There are air leaks, from the starboard cockpit locker, over the fuel tank, and through a 2" x 24" access way but if the locker is closed there is not much venting going on.There may be other air being sucked in from the bilge and through the floorboards but I can't think that would be much.

Never heard of a Valiant having air starvation issues. And they don't have blowers either, so there is no negative pressure pulling fresh air in.

I suspect the rational behind not adding a blower is that it provides a way for water to get into the boat. It's amazing how much water can flood through a 4" hole if it's 3' under water.

I have been thinking of adding one, maybe with a beckson deck plate that I can seal it up with. My engine room does get hot and there is no doubt that if it were cooler everything in it would be incrementally happier.

[JulianGullsway]

Thanks for all your answers, the point I was probably not making clear was the engine is in a virtually sealed room, correct me if I am wrong but the engine works like a huge pump and being heavily reliant on air or it will inevitably pull air in from the weakest point, be it an O ring on a filter and seeing as I have 3 filters I would assume that is were the problem is, this only happens after many hours of the engine running so it is very hot !

[Tellie]

Originally Posted by JulianGullsway

Thanks for all your answers, the point I was probably not making clear was the engine is in a virtually sealed room, correct me if I am wrong but the engine works like a huge pump and being heavily reliant on air or it will inevitably pull air in from the weakest point, be it an O ring on a filter and seeing as I have 3 filters I would assume that is were the problem is, this only happens after many hours of the engine running so it is very hot !

I would "assume" that if your engine compartment is so air tight sealed that the engine could suck air inward through an O-ring that your engines air intake would have quickly been starved of air needed to run and shut the engine down long before it even had a chance to warm up. Secondly, the engines air intake and fuel intake are two different things. If there were such an unlikely air vacuum in the engine compartment the O-ring would seep fuel outward not suck air inward. I would suggest you just haven't found the air "Ingress" to your fuel system yet. Thirdly, the most likely assumption is your engine is a diesel not gas engine. Placing a ventilating fan in a sealed gas engine compartment has to be done correctly.

[GordMay]

Engine room ventilation ➥ http://www.cruisersforum.com/forums/...ion-85829.html

Engine Ventilation: Skip it? ➥ http://www.cruisersforum.com/forums/...-it-37561.html

Engine Room Blower ➥ http://www.cruisersforum.com/forums/...wer-42656.html

[SteveInMD]

...4108 has a tendency to on occasions cut out due to air intake in the fuel and I think its down to a lack of ventilation in the engine room...

This makes no sense. If you really had low air pressure in the engine room, really low, the fuel would tend to be pulled out of the fuel system, air would not be forced in. If you had a bad fuel system seal you would find diesel leaking out.

If you are getting air in the fuel system you simply have a bad seal somewhere in the fuel system.

In a sealed box a motor would not run very long because it would use up the air in the box and then stop.

Your engine room should have a fresh air inlet (no fan), and a blower pulling air out while the engine is on. This helps cool the engine room. Hot engine room temps can cause a variety of problems including lack of oxygen in the combustion chamber. Hot air is much more "thin" than cooler air (it carries less oxygen).