Fan in the engine room

[markpierce]

The engine compartment's air intake is shown just stern of the pilothouse door. Provides plenty of the air for the 80-horsepower diesel.

[ramblinrod]

Originally Posted by 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

You shouldn't put just any old fan in an engine compartment. The boat should
already be equipped with adequate bilge blowers for the volume of the engine compartment. If not, put that on your todo
list before next survey. The surveyor will call inadequate or non certified blowers or fans (at least they should) .

Now regarding air in fuel, as others have stated, engine compartment ventilation or lack thereof has nothing to do with this.

[transmitterdan]

Originally Posted by dlymn

Did you read my whole post? the engine consumes the equivalent of 5 times the interior volume of the whole boat every hour. My guess is that the engine room is always in a slight vacuum. my little three inch inline blower is not going to change that. It's in a flexible pipe that previously would have been allowing air to be drawn in and now my blower is doing the opposite. I do run a carbon monoxide detector in the cabin. I'll tell you if it goes off

Yes, I read your whole post. Please don't do what your are planning. You can kill the crew...really!

[dlymn]

Originally Posted by transmitterdan

Yes, I read your whole post. Please don't do what your are planning. You can kill the crew...really!

Currently, the blower is exhausting the engine room, but the flexible pipe outlet is so long and so corrugated and there is actually so much resistance that pressure builds up in the pipe and air is forced back into the engine room. (air is still blowing out of the transom outlet} To please you, I will turn the blower off and allow the engine to suck in air in as many places as possible including the particular pipe and then turn on the blower when I turn off the motor in order to suck out warm air. my carbon monoxide detector is tested regularly. It's never gone off. Do you have one?
BTW Carbon Monoxide is lighter than air. This and the fact that we motor with hatches open so that there's plenty of circulation improves the likelihood that CO will not pool in the cabin.

[transmitterdan]

For gasoline engine rooms the blower performs multiple functions. It evacuates explosive gases prior to starting the engine. It also provides additional cooling air by sucking in cooler outside air in addition to the air consumed by the engine. You should use the blower(s) as instructed by the manufacturer.

[Seighlor]

MCOS suggested pressurizing your fuel system via means of a fuel pump near the fuel intake connection. Good idea. When I encountered this same problem several years ago, after many trial-and-error attempts to find a leak, I pressurized the system with very low air pressure. I placed beneath or wrapped each connection with a paper towel so that a small amount of fuel could be detected. Finally located the offending connection and my problem was resolved.

Really believe ventilating the engine compartment has nothing to do with the fuel problem.

[Capt Gill]

Originally Posted by 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.

"The primary cause of premature engine failure is excessive heat."
That's a pretty strong statement,one I'd not heard before, would you mind showing some stats, besides anecdotal ?
I have a 4-108 with exhaust fan,only use it upon shutdown.

[Capt Gill]

Originally Posted by transmitterdan

For gasoline engine rooms the blower performs multiple functions. It evacuates explosive gases prior to starting the engine. It also provides additional cooling air by sucking in cooler outside air in addition to the air consumed by the engine. You should use the blower(s) as instructed by the manufacturer.

The OP has a 4-108 which is a DIESEL.

[transmitterdan]

Originally Posted by Capt Gill

The OP has a 4-108 which is a DIESEL.

I thought he said 4108 which is a boat model. Anyway, there are other posters with gasoline engines talking about forcing air into the ER. This is a bad idea whether diesel or gasoline/petrol.

[mickt243]

here is a question...

is it possible that a mechanic was trying to explain engine room heat causing a vapour lock in the fuel pump, and the OP misunderstanding that as "air in fuel"?

[undercutter]

Originally Posted by SteveInMD

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).

This is absolutely correct. My engine manual says that the intake air temperature should not exceed 125F.

Oh and the alternator thing too.

Do not create positive pressure in the engine room.

[Squanderbucks]

If your ER has sufficient grilled openings either to the outside or to other interior spaces that do have exterior openings such as lazerette or other non living space then the running engine will pull in the air it needs. The sheer volume of air that a running engine consumes is not practical meet with moat any fan you could install. They might stir the air some but that would be about all. Exhaust fans can be helpful for removing heat either while running of after engine shutdown. Their duct openings should take air from the upper area of the ER and any intake air should be ducted to the lower portions of the ER space.

In my earlier post the intake air was not so much to run the engines but to cool the interior of the genset enclosure box. Pumping air into it has definitely helped reduce the temperature of the inside of the box. I have a temp sensor inside and have measured it both ways and it does help the genset.

[transmitterdan]

Squanderbucks,

Most of what you said is right. However, there should be some exhaust air sucked from near the bottom of the bilge. That is where dangerous vapors hang out from gasoline and propane. I know diesel fumes are not explosive but most boats have other fuels on board. Pumping air into an engine space is a really dangerous practice. Better the generator has a short life than the crew. Exhausting air will provide the same temperature reduction without risking the crew.

The worry seen in this thread about heat damaging an engine is some kind of urban myth I think. High ER heat can reduce alternator output and it can damage rubber hoses and such. But the actual engine is a big hunk of metal that doesn't much care about the air temperature surrounding it. The combustion air inlet wants to be cool as possible so it should be near an outside air inlet port. But the engine itself could care less about the ambient air temperature. Even modern electronic engine controls are designed for high ambient temps.

Some boats have things in the ER that should not be there such as battery chargers, batteries, inverters, auto pilot computer, electric fridge compressor etc.

[rourkeh]

I am reading a lot of input claiming heat in the engine room does not effect engine performance. This is absolutely not true. In my experience with larger motoryachts the design and layout of the engine room is critical during the build. Marine engines are manufactured to perform at optimal efficiency at a pre-determined temperature, excess heat causes loss in performance and reduced wear on internal components. This is a fact. The following is a good article about sailboat auxiliaries and their diminished lifespan.
Marine Engines: Sail Boat Auxiliaries at Dockside Reports

There is a huge amount of information on engine manufacturers web sites on this subject.

[DeepFrz]

Originally Posted by rourkeh

I am reading a lot of input claiming heat in the engine room does not effect engine performance. This is absolutely not true. In my experience with larger motoryachts the design and layout of the engine room is critical during the build. Marine engines are manufactured to perform at optimal efficiency at a pre-determined temperature, excess heat causes loss in performance and reduced wear on internal components. This is a fact. The following is a good article about sailboat auxiliaries and their diminished lifespan.
Marine Engines: Sail Boat Auxiliaries at Dockside Reports

There is a huge amount of information on engine manufacturers web sites on this subject.

Did you mean to say "increased wear on internal components"?