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Blowers for a diesel

4K views 20 replies 13 participants last post by  mbsl98 
#1 ·
I have a 86 Pearson 39 that i have been slowly rehabbing. I am trying to clear away some of the clutter and straighten out lazarettes etc. I have noticed that the boat has blowers located in the aft lazarette and near the engine compartment. The boat has the original Westerbeke 46. When it comes to diesels I am a novice but I thought blowers were only needed for gas engines? Is this necessary? Thanks
 
#3 ·
I don't think he means a supercharger or turbocharger. He is talking about a ventilation blower.

Yeah, my diesel has them, too. Even though, I don't think there is much danger of an explosion from diesel fumes.
 
#4 ·
You don't need then on a diesel.
 
#5 ·
However.... having a blower that runs while you run (and ideally another 10 minutes or so) will go a long way to reducing any residual 'odour' after running, and remove some residual heat in summer.

A friend's 2001 Beneteau in the tropics has a blower that stops and starts with the 'ignition' switch. I'm thinking of putting one in even though I have eliminated all leaks and odour is not an issue, heat can be in summer.
 
#11 ·
However.... having a blower that runs while you run (and ideally another 10 minutes or so) will go a long way to reducing any residual 'odour' after running, and remove some residual heat in summer.
...
Bingo.

A blower isn't legally necessary if the boat has a diesel engine. But it is nice to have.

On my boat the intake hose for the blower is in the bilge sump. If I had a propane stove or heater, which I don't, it would keep stray gas fumes from building up. As it is, the added air circulation helps to keep the bilge dry (well, drier anyway).
 
#6 ·
What Faster said, while not needed for safety like a gas engine, it will remove excessive heat. During a hot summer day you may appreciate running it for several minutes after shut down. Helps circulate some fresh air which the engine would benefit from as well

I have one to remove heat primarily because I have a battery bank nearby.

I know a few sailors whom didn't know they had blowers till several years of ownership ;)
 
#8 ·
What Faster said, while not needed for safety like a gas engine, it will remove excessive heat. During a hot summer day you may appreciate running it for several minutes after shut down. Helps circulate some fresh air which the engine would benefit from as well

I have one to remove heat primarily because I have a battery bank nearby.

I know a few sailors whom didn't know they had blowers till several years of ownership ;)
I am going to be taking the boat to So. Florida next year so maybe I will rethink the removal. Thank you
 
#9 ·
FWIW...when I re-powered I replaced the 30 year old blower, when I did...I didn't put any vent hose on it since its high in the engine room and heat rises, I didn't see the point?

Of course on a gas engine where the fumes are heavier then air and your trying to exhaust the fumes you need to run the flex vent hose low in the bilge
 
#10 ·
If there are two, one will be for exhaust, connected to a vent tube that is positioned near the high point in the engine compartment, to remove hot air. The second will blow relatively cooler outside ambient air into a vent tube (or several connected to one another at a plenum) that terminate near the bottom of the engine compartment. The cooler the air that the engine intakes, the more efficient the engine and the cooler it runs. The vent blowers do make quite a difference as others have noted, above.

FWIW...
 
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#12 ·
But, I strongly argue that any boat with a propane system should have a bilge blower. In my life time I have seen far more sail boats blow up from propane leaks than I have from having gasoline engines. It seemed like bilge blowers were standard on boats with propane systems back in the 1980's but that stopped at some point for reasons that I cannot conceive of.

Jeff
 
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#13 ·
But, I strongly argue that any boat with a propane system should have a bilge blower. In my life time I have seen far more sail boats blow up from propane leaks than I have from having gasoline engines. It seemed like bilge blowers were standard on boats with propane systems back in the 1980's but that stopped at some point for reasons that I cannot conceive of.

Jeff
I think when the Atomic 4 stopped being the de facto standard engine on auxiliary sailboats, and little diesels captured just about 100% of the market, people forgot that gasoline fumes weren't the only dangerous gas aboard. Manufactures figured they could save a couple of hundred bucks a boat by not installing blowers in boats that weren't legally required to have them. And owners who re-engined their boats either tore the blower(s) out as part of the re-engining, or never replaced them when they eventually failed.
 
#14 ·
OK? Now here's a ??
I have the (3"flex-hose) vents and "scoops" on the top of the transom; tho I don;t have a gas engine...anymore.
Would the un-fan'd vents work to refresh air in the bilge/engine compartment better than none at all??
TIA,
Paul
 
#18 ·
If the vent cowls are oriented 180˚ to each other they will probably move quite a bit of air. However, only when there is a breeze going over them, and not as much as if one were fitted with a blower.
 
#15 ·
From classes I took from a well-respected diesel mechanic:

DIESEL Engines only!

1) Run the blower any time the engine in running. Yes, really.

2) if the hose intake is anywhere else, move it to the top of the engine, and place it near to the alternator if possible. Heat is the enemy of alternators.

3) Keep the complete engine block and attachments clean, as most engines are designed to shed about 5% of their waste heat by direct radiation. That's not much, but can make a difference in hot weather.

4) Do not worry too much about air supply. Just be sure that you have air coming into the engine compartment from enough square inches of access to more than equal the size of the intake. Diesels have a truly voracious appetite for air -- they are Not going to starve.

5) If that old vent hose (aka "dryer hose" is over about 10 or 15 years old, replace it all. The vinyl gets brittle and starts breaking up. The old steel spiral wire rusts out also. It's cheap.
Those common old Atwood "turbo blowers" have a life, too, but can easily go a decade with a little luck.

6) For the least operating noise, be sure that every little crack in every part of the engine compartment that is adjacent to the interior is sealed. Any little opening will let in more noise than you would imagine.

Regards,
Loren
 
#16 ·
6) For the least operating noise, be sure that every little crack in every part of the engine compartment that is adjacent to the interior is sealed. Any little opening will let in more noise than you would imagine.

Regards,
Loren
Great post Loren.. to which I'd add (on your last point) get some self stick rubber bits and carefully go round and eliminate every rattling cabinet door, hatch cover, mast steps, whatever, everywhere on the boat. You'd be amazed at how much of your motoring 'noise' can be attributed to vibration sources.. another reason to ensure your alignment is a good as you can get it.
 
#17 ·
6) For the least operating noise, be sure that every little crack in every part of the engine compartment that is adjacent to the interior is sealed. Any little opening will let in more noise than you would imagine


But be sure you aren't truly airtight or have good air flow into the engine compartment. The engine needs it to run efficiently. I remember a story a mechanic told me about the time he got called out on a "problem" that made no sense to anyone. The guy had the engine running when he got there because no one could ever reproduce the issue. It "fixed" upon opening the access port. Diagnosis- not enough oxygen to the engine.
 
#19 · (Edited)
6) For the least operating noise, be sure that every little crack in every part of the engine compartment that is adjacent to the interior is sealed. Any little opening will let in more noise than you would imagine

But be sure you aren't truly airtight or have good air flow into the engine compartment. The engine needs it to run efficiently. I remember a story a mechanic told me about the time he got called out on a "problem" that made no sense to anyone. The guy had the engine running when he got there because no one could ever reproduce the issue. It "fixed" upon opening the access port. Diagnosis- not enough oxygen to the engine.
And that's why I referenced ONLY the parts of the engine compartment facing into the interior. There should already be plenty of air inflow from aft areas.
 
#21 ·
One more for a blower with diesel. My old Dufour 35 (1973) came with Volvo 36hp diesel and a permanently wired blower that was always on with ignition. Didn't even have an on-off switch. In line with the quality of the vessel, I have always thought that their equipment choices were pretty sound.
 
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