Running engine compartment blower when under way

seadaddler · Aug 2, 2011

Yes

Yes I have been running my engine blower any time the engine is running and I got into the habbit from my wife asking to do so because she felt it was there so use it and now I do it all the time.
I fine it helps take the heat out and when we sleep on the boat it helps with less heat in the rear berth where we sleep and my wife seems to have a sensitive smeller and always smells some kind of odor from the engine when it's time to sleep so running the blower really helps out a lot,my blower is not noiisey and can only hear it if we shut off the engine and than we shut the blower.
Nick

Snotter · Aug 2, 2011

Batteries do better when they aren't hot. Run the blower.

Maine Sail · Aug 2, 2011

I don't run it. It is there simply to meet the requirement on our boat as we have diesel. I don't find any real need to use it and our engien has a sealed engine PCV system so no odors. When I have run it, to see if it changed the engine compartment temps, I found it did virtually nothing.

Batteries should not be in an engine space anyway, this equals a super bad location for them, and if they are there it is a must that they be temp compensated.

Builders who install batteries in engien spaces that can go above 100 degrees should be taken out to pasture and "disposed" of..

If you've installed a regulator like a Balmar that can't handle engien room temps then the blower won't help it enough unless the system is expertly designed which most are not..

Perhaps 85-90% of the installed blower systems I see out there are a horrible after thought thrown in to simply meet a "requirement". I have seen many installations where the compartment is so "sealed", to cut down on sound, that running the blower actually starves the motor of air and they can begin to run sooty. On one boat the transom soot was virtually eliminated by having the owner stop using the blower. Turned out later the cheap drier vent intake had been collapsed by an errant life jacket crammed into some space below the cockpit. Other installations often lack the same intake sq. in as the exhaust. I also frequently see blowers attached to nothing as the hose has fallen off the exhaust vent so charging energy gets wasted by simply circulating the air in the bilge......

If you want cooler temps I think an intake fan and exhaust fan would be the best approach. I would aim an intake fan right at the alternator on the "intake" side, if you have a large bank, to get the most benefit. Alts that run cooler last longer and put out more current..

RAD · Aug 2, 2011

On my center cockpit the engine is right below the cockpit and the battery's are also in there along with hot water heater,fuel tank,water tank and waste tank so I installed a blower to help cool things down along with saving ice cause the one side of the ice box shares the bulkhead wall with the engine room.
My blower is set up so in comes on automatic with the engine so I don't forget and I can throw a switch to leave it run for a while when I get to a destination to cools things off the

jviss · Aug 2, 2011

As an aside, my blower has never worked, and I have no idea where it is! Anyone know where the blower motor is on a 1984 Catalina 36?

Snotter · Aug 2, 2011

Hmmm--interesting discussion. I'd like to install an engine room thermometer that I can monitor from the helm. I have to admit that I do get a sooty transom. However, I think I have a 165 deg thermostat installed when I should have a 185 deg thermostate. Also, my engine room is not very air-tight.

kloudie1 · Aug 2, 2011

Notes on engine box air.. Thumbnail numbers.. My 3 GMF displaces 880 cc. I normally cruise it at about 2800 rpm.. At this speed, it pumps about 43 Cubic Feet per Minute (CFM) of air out the exhaust .. That will change the engine enclosure air 4.5 times per minute, or once every 13 seconds.. Should not be a problem under cruise .. but when you stop, the big chunk of iron that is heated to around 200F has to give up its heat to the box and there is no air flowing..That is when it gets really hot and could use some forced ventilation.. At idle, the airflow slows so the air is changed about every 45 seconds.. I plan on putting in a three inch "Yellow Tail" blower to start as we go toward a harbor and keep it running for a while after securing the engine. At about 100 CFM it should ventilate the box sufficiently.. It draws 3.8 amperes (max) so running it for a half hour on anchor should not affect the batteries very much..
In the winter that heat is welcome.. but on that day, sometimes it rains and I don't sail. !

Old Skool Neil · Aug 2, 2011

I'm a gasser so running the blower is a matter of safety and prudent boat operation. For you diesel guys, aside from the perception of engine room cooling, the reality is many (not all) of your boats stink of diesel. This is not a slam, just the truth. It's much like visiting a home that has a pet cat. One foot inside the door and you know.

For no other reason I would run the blower in a diesel powered boat too.

kloudie1 · Aug 2, 2011

More notes, regarding gasoline engines.. Because gasoline engines run throttled, and stoichiometrically, they pump a lot less air than a diesel.. In rough round numbers, the case of an Atomic 4 running at a nominal 2000 rpm cruise, it would pump only about 9 cfm of air. (about 4.5 times less than a diesel) . It only pumps its full capacity at wide open throttle, which doesn't happen much. Another reason that blowers are better run while underway on gasoline powered vessels.

Calif. Ted · Aug 2, 2011

JVISS, Catalina almost always mounts the blower on the inside port transom within a foot of the cowl vent (exhaust) on that side. I run them whenever the engine is running and have replaced so many I can see them in my sleep.
BTW if I smell diesel inside the boat I start looking for the leak, shouldn't be any diesel smell.

Stu Jackson · Aug 2, 2011

As an air conditioning engineer, I can advise you that what most people think is helping by running the blower is, excuse me, hogwash.

Almost all boats I've seen that have blowers have an intake hose on one side and the blower on the other, not bad for starters.

But the hoses are generally thrown on the floor of the hull and may or may not end up anywhere near the engine!

In addition, if one intends to exhaust hot air, the exhaust hose, the one connected to the blower (which is an exhaust fan, BTW), needs to be above the source of heat (or odor, like in a toilet exhaust in a building or your kitchen hood at home).

Maine Sail is right, either have a blower sending air IN to the space, or forget it as a functioning system. Would be much better to have two blowers, one blowing air in, the other exhausting air.

Fumes? Diesel smells. Who'd want a boat like that?!? Fix the leak and get some PureAyre and clean up the boat.

Getting heat out after the engine has been run? See above - won't work if the hose is below the heat. Period.

Could work for "fumes" as originally built, but if there are fumes of any kind, I wouldn't start the blower or the engine!

jviss · Aug 2, 2011

Thanks, Ted, ...

... I'll look for the blower this weekend. I'd actually like to use it for moving air to my refrigerator compressor.

jv

kloudie1 · Aug 2, 2011

Correct, Stu.. my intake will be above the engine..

Don12364 · Aug 2, 2011

Kloudie and Maine are right - but so is O.S.Neil - down below diesel boats do smell (Please don't all write and say yours doesn't as I can smell it from here!)

Most boats do not have a dedicated fresh air inlet port for the engine air so it is a mystery how the engine breaths at all. This means the engine bay will be at a lower pressure than the rest of the boat and air will be being drawn in through cracks and holes for as long as the engine runs.
No smell can get out and a 40 horsepower vacuum cleaner takes a lot to deter it. Dragging air out of bilges and lockers helps keep the boat sweet anyway.
So I guess those little 1" diameter finger holes on locker lids and floorboards have a useful purpose after all.

As others have said, the time to run the exhauster is after the engine has run and whilst it sits and heat soaks and festers.

BTW you need an extractor fan NOT a blower. We call them exhausters.
Very exhausting.

Stu Jackson · Aug 2, 2011

Donalex, you're right, they call 'em blowers here even though they are exhaust fans.

And my diesel boat don't smell of diesel. Ever. I doubt if I'm unique.

RAD · Aug 2, 2011

So my setup from Oday is two forward facing cowl vents and two rear facing cowl cents with 4' flex hose on all and the two forward facing vents are down low close to the bottom and the other two which exhaust are up high, and I have a blower (exhaust fan) on one of the two
I never noticed a difference in air temperature till I put the blower in so I know the system works well and just for fun I'm going to put a remote thermometer down there and see whats really going on

Ralph Johnstone · Aug 2, 2011

I'm With You, Stu .........................................

........................ I've never had a diesel smell and never will. Just say NO to diesel leaks. And this is after 12 years on a 1999 H310.

Now, contrary to what many have said here, I'm actually PLANNING to install an exhaust fan to my engine compartment. Why ? ?

Nuts you say, off the deep end, drugs, stood too many night watches ?

Well now, take a look at the attached photo of my engine compartment. See it under the steps?, way back there?, the white shoe box?, well squint and you'll see it. There's a barely an inch of clearance around most of the Yanmar 2GM20F. Mind you, the compartment so well sound proofed it's hard to tell when the engine's running. And there is plenty of cross-sectional air inlet area but Lord does it get hot in there. All the combustion air is pulled between the floorboards and the boat hull but it just doesn't cool it by much.

I'd never really thought about this until I recently installed a Balmar ARS-5 alternator regulator. The alternator temperature sensor shows 75 deg. C (167 deg. F) when the alternator is loafing along on "float" and rises up to 85 deg. C (192 deg. F) when its really putting out on bulk charge.

Not too good for the alternator but probably even worse for the air intake to the engine. Compared to pulling room temperature air, that hot air is cutting down the oxygen input to the engine by 19%. Just not right when that little work-horse is trying to put out approx. 80% loading for hours and hours on end.

(We don't get too much wind up here in B.C.).

So there (in a nut shell) is the reason why I'm installing an exhauster

in the hopes of:

1) running my alternator a little cooler and

2) supplying cooler air to my engine air intake.

Calif. Ted · Aug 2, 2011

I couldn't stand the laughter if I asked for an EXHAUSTER at the parts counter in the US.

Stu Jackson · Aug 2, 2011

There is great merit in installing exhausters (blowers - just form the other end!

in boats with either confined or engineered-in engine compartments.

The amount of effort builders go to to prevent noise from engines is counterproductive to getting the necessary air INTO an engine space.

It's a real trade-off.

Running engine compartment blower when under way

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