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Diesel engine blower?

7K views 27 replies 11 participants last post by  sailingdog 
#1 ·
I'm thinking of installing one of those small in-line blowers to exhaust the heated air from my diesel engine compartment. I could attach it to a ventilation hose that leads aft. I believe it will help on those hot summer nights, and should keep the air fresh in the aft berth.

Is this a good idea? If so, should I run it continuously when the engine's running, or should I put it on a switch and turn the blower on after running the engine?
 
#3 ·
I have it too, in fact, even with a Diesel engine its mandatory by law in the European Union.

I have an inline (had a centrifugal impeller one, but was too heavy and noisy, so I removed it), made by vetus, and its on when the engine is on. It helps recirculate air inside the engine compartment and removes the hot air.

Its good to dry the shoes also.....
 
#4 ·
When the engine is running, it should be sucking in enough air (which is simply taken from the engine compartment in small boats) to keep up good airflow. The real value with a diesel engine is when the engine is shut down, the forced air from the blower will cool it down faster, which prevents the engine oil from cooking and tarring, and taking the heat out of the boat keeps you cooler as well.
As an exhaust for the afterberth it might be excessive--engine blowers usually are high velocity and noisy. For a berth you are better off with a low velocity high area (i.e. large and slow) fan.
 
#5 ·
I think it's a great idea, as long as you are sure you will still have adequate air intake to the engine box to run the engine. The fan will remove heat more quickly, and also perhaps help to minimize the inevitable odors that manage to sneak out into the cabin space after a long run.

I'd run the fan all the time the engine runs, and perhaps with an off-delay timer so it runs a minute or two to exchange the engine box air a time or two after shutdown.
 
#6 ·
I have read (but don't really know) that some blower motors are not designed to run for long periods of time--ie. anytime the engine is on. Others apparently are designed for continuous, longer term operation. Does anyone know if that's true, and which ones are short/long term use?
Frank
 
#10 ·
"How about an electric thermostat?"
More stuff to break?<G>

Actually, if your engine block has a spare thread tapped in it, you can use a standard automotive fan switch--perhaps with a manual blower bypass. They typically come on between 170-200F which is not ideal for a raw-water cooled diesel but might be good enough.
 
#11 ·
Most of us probably know why a gasoline inboard needs a blower, right? Diesels are not known to blow the top of the boat off unlike their gasoline guzzling redheaded stepchilds do. Why bother with a blower? Is it really necessary? Do you really motor that much? Why have a sailboat if the engine and hence the motor is constantly running? Go on ahead to the dark side, go to the land of See Ray. With that said, I do have a blower because PSC or ???? installed it. I put a switch on the circuit due the unbelievable racket that the little air pusher produced. Oh well, folks in glass houses shouldn't throw parties, right?
 
#12 ·
Rick-

There are many reasons that installing a blower in a diesel engine compartment make sense.

1) It helps the engine breathe properly
2) It helps vent excess heat from the engine compartment, and can help keep the boat cooler in the summer time.
3) It helps keep the smell of the engine out of the interior of the cabin
4) It helps keep the alternator cooler, which will increase its efficiency and extend its life.
 
#13 ·
sailingdog,
I guess we can agree to disagree on this one. My sailing, not motoring for extended periods of time, occurs in fresh northern waters with cool to cold water. My engine compartment is not airtight and for a little 3 cylinder diesel needs no additional air. I have no smell, if I did then I have an engine problem, leaking fuel, leaking exhaust or leaking oil that would need to be addressed and corrected. The altenator is designed for engine heat. I have not had a problem nor do I expect one with the current setup.
 
#14 ·
As for me, I will install my blower tomorrow. I look forward to a cooler aft berth, and the elimination of the slight smell from my 20-yr old engine that seems worse on hot days.

Yes, it's a sailboat and I am a sailor, but I am not ashamed to crank up "Ol' Bessie" when I need to.

As I think about tomorrow's installation, the numerous possibilities have me reeling. I'll attach the blower to the existing 3" duct pipe that leads to an aft cowl. I think I'll run the power and ground lines through the main panel to a dedicated switch, but I wonder if I should run the hot wire to the ignition circuit so the fan runs with the engine? Any advice there? Also, Should I run a separate switch to the cockpit? Where in the line should I put the fuse?
 
#15 ·
You really need to consider which blower and how to plumb it. I've installed many for customers, but all were on big powerboats that began to suffer for horsepower in steaming hot Naples. As engine room temperatures soared, horsepower fades because the engine intake air is less dense and expands less in combustion. I used the inline 4" blowers to take air from outside and blow it straight at the engine air intakes, resulting in the engines again being able to make proper peak RPM's to get up on plane. The blowers are keyed to the engine 'run' position through constant duty solenoids. Engine room exhaust is not blown, but is ducted out from as high in the engine compartment as possible to get the hottest air first. An auxilliarly switch can be rigged on the console to cool the engine room after shutdown, but it should be either set on a timer or be accompanied by a large, annoying red light to keep you aware that it is on.

In a tight engine room, air in equals air out and engine combustion is a large part of that process, so the blowers on a big powerboat cannot possibly keep up with two big diesels at full song, though they do help performance. In a sailboat with less than 100 HP (most have 30 - 60) a single 4" blower is more than enough. I have a tendency to treat horsepower and engine health first, and engine room ventilation as a happy by-product. It still works.
 
#16 ·
RickBowman said:
sailingdog,
I guess we can agree to disagree on this one. My sailing, not motoring for extended periods of time, occurs in fresh northern waters with cool to cold water. My engine compartment is not airtight and for a little 3 cylinder diesel needs no additional air. I have no smell, if I did then I have an engine problem, leaking fuel, leaking exhaust or leaking oil that would need to be addressed and corrected. The altenator is designed for engine heat. I have not had a problem nor do I expect one with the current setup.
Works for me.. but just because an alternator can work in a hot environment, doesn't mean that cooling that same environment won't make the alternator work better and last longer.
 
#17 ·
Rick-
"The altenator is designed for engine heat." Ideally, yes. But if you look at the service bulletins and installation notes for alternators in general? Reality bites. A marinized alternator needs dual fans to compensate for not having the generous airflow that a car or truck has. Not all conversions get that right. And even then, as an alternator (or most other electronics) runs hotter, the time between failures goes down, the output goes down...An engine can run damn hot, remember the block is trying to run at thermostat temperature (140-180F) and the the side near the exhaust manifold will be running in heated air as well.

Not that I'd run a bilge blower all the time to cool the alternator! Just pointing out that alternators, like other valued household staff, perform better as they get closer to 74F.<G>
 
#18 · (Edited)
sailor25b said:
I could attach it to a ventilation hose that leads aft.
Think about where that hose goes through the boat?

Arguably, one of the best places would be in the cockpit under something, so that if caught in rough seas water does not easily enter through the opening. A 4" hole could fill a boat pretty quickly :eek: You can see were mine in this photo link, located just to the right/bottom of the engine gages

click link for image:

http://newimages.yachtworld.com/1/5/9/8/7/1598774_6.jpg?1158931582000
 
#21 · (Edited)
hellosailor said:
T37-
"A 4" hole could fill a boat pretty quickly" You mean, everybody doesn't have ball valves or fill plates handy, to secure their engine compartment vents in rough weather?! <G>
I was trying to imply is that the transom/stern is not a good place to cut a hole so large, as you see on allot of powerboats for instance.

Ball valve's on a blower? please explain...:confused:
 
#24 ·
Generally, most of the blower duct output for the engine compartments that I've seen on sailboats are located under a coaming of sorts, in the aft end of the cockpit, and use a dorade-type cowl to prevent water from coming into them.
 
#26 ·
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