Engine blower motor

[deluxe68]

Originally Posted by Dockhead

This is an awful lot of convolutions to try to get at -- what?


The proposition of not blowing air into engine rooms is a much simpler concept. You want to move air through the ER in order to keep temps down. Right? How do you want to move it? If you suck it, you keep pressure down, enhancing the engine's effect, keeping fumes, heat, etc. inside the ER rather than getting it into the passenger space. If you blow air in, rather than sucking it, you will be working against the engine and reducing the beneficial effect of keeping pressure down, in the best case (in the worst, you will overcome this effect and create overpressure). This is a very simple concept, and the reason why no actual engineer in the world would blow air into a sailboat engine room. All this business about positive displacement and squirrel cages is noise -- whatever the efficiency loss in the blower, 10%, 20%, 50%, even 90% -- every cubic meter of air blown in, will be creating an undesirable effect of one degree or another, and for what? What's the point?


As to concrete cases -- every sailboat I've ever seen, from a Catalina 27 to a Swan 90, other than those with ER in a separate watertight compartment (Sundeer 64, Amel 53), drew air into the ER through the bilges, not through separate ducts from the outside. If you end up with overpressure in the ER, it is a very not good thing. Fumes and heat will come out through the bilges, and also I've never seen an ER which was perfectly air tight, so there will be leakage from other places as well.


Why all this? Just suck, don't blow. I don't know what's so hard to understand about this.

My boat has a small louver just above the engine compartment used for intake.

[Dockhead]

Originally Posted by deluxe68

My boat has a small louver just above the engine compartment used for intake.

That's interesting; thanks. But doesn't the ER communicate as well with the bilge?

[deluxe68]

Originally Posted by Dockhead

That's interesting; thanks. But doesn't the ER communicate as well with the bilge?

Yes, the engine compartment is open to the bilge. But the air has to get into the boat somehow. I have two sets of louvers on the boat, one set above the engine by the companionway and another (larger) set on the combing at the transom. The engine exhaust fan exits air thru the transom but I am not sure if it uses both of the louvers at the transom or just one.

[Dockhead]

Originally Posted by deluxe68

Yes, the engine compartment is open to the bilge. But the air has to get into the boat somehow. I have two sets of louvers on the boat, one set above the engine by the companionway and another (larger) set on the combing at the transom. The engine exhaust fan exits air thru the transom but I am not sure if it uses both of the louvers at the transom or just one.

So the companionway louvres let air into the salon, or into a duct which goes into the ER?


In either case, this turns out to work more or less like other boats. Air comes into my boat (to make up air drawn out by the ER fan), via 6 large dorade vents.

[deluxe68]

Originally Posted by Dockhead

So the companionway louvres let air into the salon, or into a duct which goes into the ER?


In either case, this turns out to work more or less like other boats. Air comes into my boat (to make up air drawn out by the ER fan), via 6 large dorade vents.

The companionway louver is ducted into the engine compartment.

[hikersailor]

I replaced both of my engine room blowers with standard blowers for boats. However if I did it again I would look into a 12 volt squirrel cage design if available. Much quieter and mows plenty of air and possibly less amp draw.

[jonarck]

The Plastimo blower is $195 from SailorMan in Ft. Lauderdale.

I was going to get a Jabsco for $90, but the mounting holes didn’t line-up and trimming the plastic base for new holes wasn’t feasible and new holes would have gone-beyond the stainless vent’s dimension m.

Cheers,
Jon Arck
Leopard 44 Second Star
North Palm Beach, FL

[Beau.Vrolyk]

One of the most temperature sensitive items in the engine room is the high output alternator. If possible, run an outside air duct to a place just behind the alternator so that the cooling fan on the front of the alternator can draw cool air through it.

Most diesels will not suffer from breathing hot engine room air until the inlet temp gets really high. EG: >170 deg F. Even then, you will simply reduce the power output and make the motor less efficient. Many other things, like the water maker, will suffer before the diesel does.

For grins, put your hand behind the exhaust pipe and compare the flow to what your blower puts out. Generally, you’ll find the diesel move vastly more air than your blower because it is a positive displacement pump while blowers are not. As a result, the output of the blower declines rapidly with head pressure, while the diesel dose not.

If possible, having an engine air inlet which is outside of the engine room is helpful, provided it can’t swallow water.

[wackerb]

In all these posts I think water was only mentioned once. With a much higher specific heat and circulating directly through the engine why isn't that enough to cool it? On my Lagoon catamaran with 40 hp Yanmars each engine intakes 2 - 4" air and 1- 3" blower (suction) vent to the transom with a cover which allows lots of water to enter all of them. After multiple replacements of broken covers which take a real pounding from waves as well as allowing water into the vents I made fiberglass covers which were a little tighter and have not broken, but water still enters the air hoses. With 2 engines one blower never worked. I did a test of blocking all the air hoses and running the engine with some flimsy plastic over another opening into the engine compartment and could detect no negative pressure since it is open to the bilge and the rest of the boat. So the 2 - 4" intakes seem superfluous. To stop the water entry I sealed off all the vents and disconnected the blowers. I think the engine is cooled sufficiently by water which also limits the compartment temperature, but I guess I should check the air temp to be sure.

[a64pilot]

Originally Posted by Dockhead

That's interesting; thanks. But doesn't the ER communicate as well with the bilge?

Other than leaks that is where all the air to my engine room comes from, which means all air comes from within the boat.
Oddly though with everything closed up, you don’t even notice a breeze from the companionway, bu that has to be where almost all the air that is being sucked out, comes in at. I don’t have dorade vents and I’m talking when the boat is closed up, as in it’s cold outside.

[Dockhead]

Originally Posted by Beau.Vrolyk

One of the most temperature sensitive items in the engine room is the high output alternator. If possible, run an outside air duct to a place just behind the alternator so that the cooling fan on the front of the alternator can draw cool air through it.

Most diesels will not suffer from breathing hot engine room air until the inlet temp gets really high. EG: >170 deg F. Even then, you will simply reduce the power output and make the motor less efficient. Many other things, like the water maker, will suffer before the diesel does.

For grins, put your hand behind the exhaust pipe and compare the flow to what your blower puts out. Generally, you’ll find the diesel move vastly more air than your blower because it is a positive displacement pump while blowers are not. As a result, the output of the blower declines rapidly with head pressure, while the diesel dose not.

If possible, having an engine air inlet which is outside of the engine room is helpful, provided it can’t swallow water.

Indeed the alternator is the device which most people worry about, temperature-wise, but not indeed HIGH output alternators, but low output ones. High output alternators, especially large frame ones, work just fine in high ambient temperature. It's small frame car type alternators, not designed for producing bulk power, which have thermal problems.




As to "positive displacement pumps" -- this has been discussed, but you can't say that one pump "moves vastly more air" than another, just because it is one type, rather than another. It depends on the relative size of the pumps and the resistance of the outlet. A specific example was named -- the standard Jabsco ER blower which moves 7 m3 per minute nominally. Even if it loses HALF of that volume due to a badly designed outlet duct, it's still moving more air than a 2 liter diesel engine running at redline.

[Jimmyhenry]

Without a bilge blower the engine room will have negative pressure. Probably about the same as running a diesel at altitude. They hate that.
And without a blower any fumes in the engine room will be gone quickly out the exhaust.
So having a blower drawing air out of the ER and making the engine suffer even more, beggars belief.

More important is keeping the alternator cool. And here a small blower directed at the alternator “suck” side is best.

[SV Xpensive Care]

Originally Posted by JohnB40

Hi
Have a Beneteau 40, 4JH4AE Yanmar.
There is a Plastimo air blower on the transom to extract hot air from engine compartment. Stopped working. Took apart and see the small 4 amp 12V DC motor is labelled Von Weise, made in Canada, 2807-506-006. Motor is fried. Rather than pay about $300 for blower replacement I would like to replace just motor which seems to cost about US$50 ... if you can find it. I have found a motor that has same measurements (Kysor 2807-506-032) but that is apparently not quite right as is two speed ... that one is US$50.
Has anyone any idea where I can find this motor ... I've searched the web but I'm not very good at that ... sort of a dinosaur!!!
Cheers
JohnB40

Try this . . .
Von Weise of Canada
Von Weise does not handle the Von Weise of Canada Company motors originally produced in Canada. Please send inquires to mwilk@dcm-mfg.com

[a64pilot]

Originally Posted by Jimmyhenry

Without a bilge blower the engine room will have negative pressure. Probably about the same as running a diesel at altitude. They hate that.

And without a blower any fumes in the engine room will be gone quickly out the exhaust.

So having a blower drawing air out of the ER and making the engine suffer even more, beggars belief.



More important is keeping the alternator cool. And here a small blower directed at the alternator “suck” side is best.

It’s almost certainly less than being at 100’
Be real easy to measure, all I’d have to do is ask my Son to bring an altimeter with him this weekend. Actually all you need is a barometer, most of us have one right? Put it in the engine room and crank her up. each .1 in if of mercury is equal to about 10 Ft. So 29.92 to 29.82 is about 100’.
Just thinking but if there was much difference in pressure, you would never get the engine room open, it would be sucked shut, and I’ve never noticed a difference, have you?

[Jimmyhenry]

Originally Posted by a64pilot

It’s almost certainly less than being at 100’
Be real easy to measure, all I’d have to do is ask my Son to bring an altimeter with him this weekend. Actually all you need is a barometer, most of us have one right? Put it in the engine room and crank her up. each .1 in if of mercury is equal to about 10 Ft. So 29.92 to 29.82 is about 100’.
Just thinking but if there was much difference in pressure, you would never get the engine room open, it would be sucked shut, and I’ve never noticed a difference, have you?

Maybe if the engine room was sealed like a refrigerator. Bit unlikely. Our engine room has heaps of openings and we never get any fumes when under way.