Engine blower motor

[Lepke]

If this is your blower, it's just a flanged bilge blower. The SeaFlow is about $45 on ebay. There are other sizes and styles.
Usually items like bilge blowers don't have extra motors made as spare parts. Whoever made the blower probably doesn't want to sell to the public.

[steve77]

A related question - Our blower is very noisy, meaning I can hear it easily even over the noise of the engine. Are the high dollar units appreciably quieter? Ours is a three inch in-line blower similar to the yellowtail from Defender. It's very old, probably 20 years or so.

Cheers!

Steve

[Bean Counter]

As noted in a previous post, care should be taken to get a "continuous duty" electric motor vs "intermittent duty" - this duty cycle is often in the spec sheets of good quality motors. Continuous duty motors are more expensive.

[rourkeh]

For the person who has never seen a $300 blower. I have 2 of these on my boat and they are the least expensive blower motors Delta T Systems sells.
https://www.boatownerswarehouse.com/...tatblowers.htm

[jimbunyard]

Originally Posted by Dockhead

7 m3 per minute blower vs 3 m3 per minute a 2000cc diesel at 3000 RPM? Or less than 1 m3 per minute at idle?

If you want to choke on fumes, just reverse your blower.

That being said, however, the main engine on my boat keeps the ER reasonably cool in cool weather, without the blower going. A couple m3 per minute is a fair bit of air.

My math or physics may be wrong but 1 m3 seems to equal one million cubic centimeters, 100 cm x 100 cm x 100 cm = 1,000,000 cubic centimeters. That would seem to make a 2 liter engine at 1000 rpm exhaust just a bit less than 2 m3 per minute, 2000 cc x 1000 rpm = 2,000,000 cc or 2 m3, minus the fuel added for combustion.

Also, 'nominal' has different levels; a combustion engine is a positive displacement pump, a centrifugal blower is not. The differences in 'nominal' for the two in this case are likely to be very large, with the centrifugal pump having a much more variable output in response to dynamic environmental conditions as compared to the engine.

Therefore, the selection of the proper blower and its' orientation (positive or negative) is dependent on the individual requirements idiosyncratic to each application...

[DougR]

[QUOTE=jimbunyard;2731169]My math or physics may be wrong but 1 m3 seems to equal one million cubic centimeters, 100 cm x 100 cm x 100 cm = 1,000,000 cubic centimeters. That would seem to make a 2 liter engine at 1000 rpm exhaust just a bit less than 2 m3 per minute, 2000 cc x 1000 rpm = 2,000,000 cc or 2 m3, minus the fuel added for combustion.


Most small two liter yacht engines are 4 stroke engines, so they only suck air in (or exhaust out) once every two crankshaft revolutions....

DougR

[jimbunyard]

[QUOTE=DougR;2731181]

Originally Posted by jimbunyard

My math or physics may be wrong but 1 m3 seems to equal one million cubic centimeters, 100 cm x 100 cm x 100 cm = 1,000,000 cubic centimeters. That would seem to make a 2 liter engine at 1000 rpm exhaust just a bit less than 2 m3 per minute, 2000 cc x 1000 rpm = 2,000,000 cc or 2 m3, minus the fuel added for combustion.


Most small two liter yacht engines are 4 stroke engines, so they only suck air in (or exhaust out) once every two crankshaft revolutions....

DougR

Oops...

[a64pilot]

Engine room blowers in a Diesel Boat are to exhaust heat, not so much as to create a negative pressure area.
No matter what kind of blower you put in an engine room, it’s not going to form enough of a negative pressure to affect the engine.

OK I was shown a $300 blower, but is a $300 blower really necessary?
I think mine was less than $50, it’s just an In-line blower though doesn’t move nearly as much air as a squirrel cage blower.

[Dockhead]

Originally Posted by jimbunyard

My math or physics may be wrong but 1 m3 seems to equal one million cubic centimeters, 100 cm x 100 cm x 100 cm = 1,000,000 cubic centimeters. That would seem to make a 2 liter engine at 1000 rpm exhaust just a bit less than 2 m3 per minute, 2000 cc x 1000 rpm = 2,000,000 cc or 2 m3, minus the fuel added for combustion.

Also, 'nominal' has different levels; a combustion engine is a positive displacement pump, a centrifugal blower is not. The differences in 'nominal' for the two in this case are likely to be very large, with the centrifugal pump having a much more variable output in response to dynamic environmental conditions as compared to the engine.

Therefore, the selection of the proper blower and its' orientation (positive or negative) is dependent on the individual requirements idiosyncratic to each application...

First of all, a 2000cc motor does indeed pump 1, not 2 m3 per meter, less volumetric efficiency losses. If it's a four stroke. Four stroke engine needs TWO revolutions to pump its displacement.

Second - positive displacement is neither here nor there. The rated flow already takes that into account. Depending on the installation, the blower might have a bit more efficiency loss than the engine, but it's not going make an enormous difference.

By all means - if you have a really big engine, and a really tiny blower, you might get away with blowing, rather than sucking air through the ER. But why set up the blower to work against the engine, rather than with it, in keeping fumes out of the passenger space? It makes no sense.

The specific blower I linked to, the one I actually have on my boat, moves 7m3 a minute. As much as two 7 liter diesels at 1000 RPM, and more than they would move at idle.

[rourkeh]

If you want to understand why you need a very good continuous duty high volume blower motor for your engine room this is a very good article that explains the topic. It is not just about removing hot air, it is about introducing cool air to operate and maintain the proper engine operating temperature range if you want your engine to last more than a few thousand hours.

Marine Engines: Sail Boat Auxiliaries at Dockside Reports

[Keelcooler]

My original 50 year old jabsco flange mount blower still works.
Squirrel cage has been rubbing on the housing for two years so it’s time to replace.

Low cost blowers are made for gas boats. Five minute run to vent motor box prior to start. No continues duty!

Leave it on and it gets very hot. Go with the jabsco. You get what you pay for.

[jimbunyard]

Originally Posted by Dockhead

First of all, a 2000cc motor does indeed pump 1, not 2 m3 per meter, less volumetric efficiency losses. If it's a four stroke. Four stroke engine needs TWO revolutions to pump its displacement.

Second - positive displacement is neither here nor there. The rated flow already takes that into account. Depending on the installation, the blower might have a bit more efficiency loss than the engine, but it's not going make an enormous difference.

By all means - if you have a really big engine, and a really tiny blower, you might get away with blowing, rather than sucking air through the ER. But why set up the blower to work against the engine, rather than with it, in keeping fumes out of the passenger space? It makes no sense.

The specific blower I linked to, the one I actually have on my boat, moves 7m3 a minute. As much as two 7 liter diesels at 1000 RPM, and more than they would move at idle.

As DougR noted previously...

Oops.

But if you think

"Second - positive displacement is neither here nor there."

I suggest you put a board over the intake of your engine and then one over the intake of you blower and see what happens.

Again, the selection of a blower motor should be made based on the specific application's dynamics.

[Zai]

Here are the specs. right from Defenders web page, of the Shurflo 30 dollar model.

Note it is continuous duty.

[deluxe68]

My current engine blower is not connected. There is a 3” duct that should connect to a 2.5” tunnel in the stringer and come out under the engine. At some point it was disconnected from the stringer and now pulls air from the under-floor area aft of the engine.

My plan is to reconnect the 3” line to the stringer opening (2.5”) and run a 2” (or 2.5”) hose up to the alternator to help cool it down. I have been searching the internet and have not been able to source short (under 10 feet) sections of high temperature flexible hose or duct. What are the temperature requirements for an engine compartment? 300 degrees?

The last time on the boat I forgot to look under the engine, I am not sure if there is enough room under there to run the 3” hose without going thru the stringer.

[DeepFrz]

I suspect that the more expensive blowers are made safe for gasoline powered boats, therefore shielded at the brushes and bearings.

In all of these discussions there is very little mention of inlet venting. The inlet air can be ducted from a vent to blow cool air on the alternator and doesn't need a blower motor as engine and exhaust blower will draw in the cool air..