Running bilge blowers?

sbw1 said:
I'm not an engineer either but wonder if engines draw air from nearer the top of the bige you would be safe thinking the fumes are evacuated with engine draw. My understanding is gasoline fumes, if present, accumulate in the lowest areas of the bilge which could be stagnant absent a bilge blower.
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You have to account for convective effects like the air being drawn in being colder and denser than the existing bilge air which is warmer. It's possible to my non-engineer mind that cold vent air may sink and displace warmer low areas of the bilge, as well as the general convective effects of local heating of the air near the engine.

IMHO, it's one of those things that takes PhD math to model and is best done via real world experiments marking the interior air with a colored vapor/smoke type substance and watching it on camera to see which areas clear faster.
 
Where does the bilge air enter? If it comes in via the blower hoses, it would enter low in the bilge and cause air disturbance. This should be enough to keep the air in the bilge circulating. Theoretically you should have no stagnant air and the air consumed by the engine will be replaced by the air via the blower intake. If this is not true, then how does a blower help?
I have seen this used on industrial turbines to cool their noise (and explosion) containment enclosures.
 
I have always run the blower before starting, while running the generator and below 1600 RPMs, basically once out of the marina, the blower is turned off unless the generator is on. This is what the delivery captain told me on my first boat and have always followed that process.
 
I always run with them on...better safe then sorry. Even now that I have diesels, I run with them on. I have been told by fellow diesel owners I don't need to run my blowers since we don't have combustible fumes in the ER, and maybe I'm the ignorant one here, but again would rather be safe then sorry. There's a reason they were installed on the boat.
 
While the 'theoreticals' are being swatted around concerning the engine breathing being able to ventilate the engine space....
Gasoline fumes, whatever the source, settle to the lowest part of the bilge. The engine intake is at the top of the engine space, so if the fumes are going to get sucked into the intake, they have to pass by the 'spark' plug wires that lie between :grin:
 
When I run a gas boat, I usually know very little about it except that it needs to be run and a mechanic has worked on it recently. I never start the engines until I open the hatch, get in the bilge and smell for gas fumes, then I start the bilge blowers and proceed with the start up prechecks. The last thing I shut down when I get back to the slip are the bilge blowers.
 
Stee6043 said:
They may be cheap but it takes three priests, two rabbis and one small child to reach them...at least on my boat. It's almost as bad as trying to add fluid to my trim tab reservoir...
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Maintainability is high on the list of any boat I consider. Hence why when I open the Engine compartment, if I can't maintain it within reason the boat gets marked off the list.
 
mnm99 said:
As I mentioned, anyone ever hear stories of explosions while at idle cruise? I'm not saying I won't turn them on, just looking for some facts.
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A few years ago a member of the yacht club I belonged to at that time had fueled his boat. Didn't turn on the blowers, started the boat and had idled about 50 yards when the boat blew up. It seriously burned a female passenger and threw her into the water. She survived but was badly burned and scarred over much of her body. The owner of the boat was also thrown into the water, burned but not as seriously as the female.

The boat burned to the water line and sank.
 
Gofirstclass said:
A few years ago a member of the yacht club I belonged to at that time had fueled his boat. Didn't turn on the blowers, started the boat and had idled about 50 yards when the boat blew up. It seriously burned a female passenger and threw her into the water. She survived but was badly burned and scarred over much of her body. The owner of the boat was also thrown into the water, burned but not as seriously as the female.

The boat burned to the water line and sank.
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Although I'm in the "run 'em if you've got 'em" camp, I wonder if this situation resulted more from not running blowers during/after fueling than from idling conditions? As in, if he'd gunned it instead of idling, would that have prevented the explosion?

My interpretation of mnm99's question is a situation where fueling the boat isn't part of the equation: if an operator uses the blowers pre-ignition and while at idle speed, turns off the blowers while running at higher speed, then drops to idle speed but doesn't turn on blowers, what's the chance of an adverse event? What happens if an operator uses the blowers pre-ignition, but turns them off while at idle speed?

Not arguing--truly munching the details of semi- and not-so-scientific "what if" modeling.
 
It is not lawyer driven.

When I was younger a friend didn't run blowers. Gas fumes lit up. One person was in the burn unit for months, still has the scars today. Others on the boat had 3rd degree burns.

If you have a gas powered boat - fume collection and explosion is a very real concern and does happen.

Mark
 
I never turn on my blowers...


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almostenuff said:
I never turn on my blowers...
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A few weeks ago I ran a boat with 3126's for about 2 hours in 90º heat. When we came back into the marina people started asking my why I was running the blowers. When I put my hand over the blower exhaust port it felt like a hair drier! I just figure it's a simple way to expel some of the heat that otherwise just builds up and slow-cooks the batteries, charger, the cockpit sole, the glue on the insulation on the underside of the deck and hatch among other things that don't like heat...
 
Gofirstclass said:
A few years ago a member of the yacht club I belonged to at that time had fueled his boat. Didn't turn on the blowers, started the boat and had idled about 50 yards when the boat blew up. It seriously burned a female passenger and threw her into the water. She survived but was badly burned and scarred over much of her body. The owner of the boat was also thrown into the water, burned but not as seriously as the female.

The boat burned to the water line and sank.
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That's not AFTER he had it on. He never turned it on. I always turn it on for 5 min after fuel and initial start.
 
RollerCoastr said:
A few weeks ago I ran a boat with 3126's for about 2 hours in 90º heat. When we came back into the marina people started asking my why I was running the blowers. When I put my hand over the blower exhaust port it felt like a hair drier! I just figure it's a simple way to expel some of the heat that otherwise just builds up and slow-cooks the batteries, charger, the cockpit sole, the glue on the insulation on the underside of the deck and hatch among other things that don't like heat...
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That seems to make sense and is certainly a conservative action that assumably wouldn't hurt anything. Unless of course it's sucking the heat back down-I'm no engineer. I deal with 700°C engines everyday, but they get a lot of airflow...


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C'mon you guys. It looks like some of you are trying to justify NOT running your blowers and for the life of me I cannot figure out why. When I had gas boats the blowers were the first thing I'd turn on when I got on board, or in the case of my trailerable boat, the first thing I'd turn on when we got to the boat ramp. They were always the last thing I would turn off.

I guess I should turn the question about whether or not to run blowers to this: WHY IN HELL WOULD YOU NOT run them. Are you afraid of the cost of replacing them?

Jeeeesus, it could cost someone their life or health if you're trying to save a few bucks.
 
I agree and keep mine on all the time, although I suppose the case can be made to only keep it on when necessary - which to me means only turning off when on plane - so they can last longer. IE; the thought that if I always leave the blower on then one day it may burn out when I do need it while out boating, whereas if I don't run it all the time then maybe it will last more years and won't burn out at an inopportune time next season(?)

As for me, I don't trust my memory 100% to turn on and off as the situation dictates.... a lot simpler for me just to leave it on all the time.
 
Gofirstclass said:
C'mon you guys. It looks like some of you are trying to justify NOT running your blowers and for the life of me I cannot figure out why. When I had gas boats the blowers were the first thing I'd turn on when I got on board, or in the case of my trailerable boat, the first thing I'd turn on when we got to the boat ramp. They were always the last thing I would turn off.

I guess I should turn the question about whether or not to run blowers to this: WHY IN HELL WOULD YOU NOT run them. Are you afraid of the cost of replacing them?

Jeeeesus, it could cost someone their life or health if you're trying to save a few bucks.
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I should clarify that I'm not justifying not using them. I was merely relaying some "wisdom" and its justification about engine air consumption providing defacto airflow through the engine compartment. The math suggests engine speeds much above 1000-1500 RPM is actually the same or more air flow than the blower alone, although as others point out there can be some suboptimal engine room circulation factors that make blowers advantageous even at that threshold engine speed.
 
hakunamatata said:
I always run with them on...better safe then sorry. Even now that I have diesels, I run with them on. I have been told by fellow diesel owners I don't need to run my blowers since we don't have combustible fumes in the ER, and maybe I'm the ignorant one here, but again would rather be safe then sorry. There's a reason they were installed on the boat.
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On diesel boat, running blowers is about maintaining a lower temperature of the air drawn in for combustion. The hotter the air, the less dense it is (less O2 molecules per cu ltr) creating a less efficient combustion cycle. Results in less power, uncombusted fuel, dirtier injectors, etc. The effects aren't drastic but impact over the life of the engine. Recreational boaters with typical hours per season wouldn't see effects or are likely to attribute to other factors.
 
Boats explode during or right after fueling....why is that? what is the source of the vapors? If the only reason a boat doesn't blow between fuel fills is because the blowers are run continuously I'd suggest there is some negligent/ignored/deferred maintenance and a captain with a poor sniffer.
 
I run my blowers continuously regardless of speed.

I also agree with Woody that most of the explosions seem to have occurred during/after refuelling. Personally, I dont check my bilge after refuelling but maybe I should as this seems to be when the risk is the greatest. I've also thought of getting a gas detector for the bilge.
 
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