Bilge blowers - Do you run them all the time?
 

Ive had outboards or diesels for a while but I'm getting back into a petrol sterndrive. Previously with inboard petrol I'd open the hatch and run the blowers for 3-4 minutes then start engines, run a minute or two before closing the hatch and I'd turn OFF the blowers. I'm now thinking that as long as the engine is running, shouldn't the blowers be turned ON?

Petrol fumes are heavier than air so with the hatch closed, any petrol fumes are 'trapped' in the bottom of the engine bay, so blower intakes are located low down.

Maybe a stupid question but do you run your bilge blowers all the time?

RR

I open the hatch to give a check, Turn blowers on for a minute or so, start engine, lower hatch. The only other time i keep them on is while refueling.

Same here!

I don't run them as much as I probably should... definitely have never run them while running on plane.

Never had an issue but I probably should make it more of a habit.

I run the blower for a few minutes, start motor, then turn it off once I start moving. One less moving part I have to worry about now that I have OB's.

Run em. Those things are cheap to replace when they wear out, so run the dog piss out of em. Ain't going to hurt a thing.

Formula does not have the greatest venting so I run mine all the time to keep the engine room temperature down. Jeff wurl

I tend to run mine a little more often when it's really hot/humid - especially when idling in to a bay for a raft up (hopefully helping to cool bilge/engines somewhat). Damn 700's and vapor lock .

As long as you make sure they are on a fused circuit, which of course they should be whoever installed them. I have seen them melt/smolder before. But yes, run them at every start up; and visually inspect the bilge every new day of boating, or after every longer break. (After a raft up, after a meal, anything over an hour or so.)

So are a lot of you guys actually running them all the time? I guess I never considered it could help with engine bay temps

I run mine anytime I'm not on plane.

I run outboards now but I ran them all of the time in my Cigarette and Formula. I still run them all the time in our MasterCraft too.

I run em before firing up and while fueling.

This thread reminded me to buy a new Xintex fume detector with automatic blower control. My last one was so sensitive it detected an exhaust manifold leak; its ten years old and needs replacing. It can false alarm when the wind is coming from the stern at low/no speed. But easily silenced and blower will run.
Gasoline Fume Detectors | Fireboy-Xintex

Should be mandatory equipment IMO

Hate to start this debate but......

Blowers should be off while fueling!!! So should all electronic devices, bilge pump, etc. and close cabin door and all hatches. When fueling is complete hang around the dock for a bit while paying, don't be in a hurry, open engine hatch, and cabin, smell for fumes, look for gas. If all clear, then it is o.k. to run blower, bilge, etc., prior to starting.

I second that. Anytime not on plane for me. Usually end up leaving it on while running regardless....

there is some running the blower all the time info in this thread
http://www.offshoreonly.com/forums/g...rving-air.html

a visual check and sniff around, then run it for a couple minutes was all i ever did, (partially because of the jack offs at the ramp), (the guys who start the engine while backing in the water then bangin it into gear and jammin the gas and mother effin every else) theres a thread on those guys too
but a consistent by the numbers pre flight probably isn't a bad idea considering the consequences.

been meaning to remind you to post pictures of the new boat, especially those engine room hatch vents (inside and out)
bet your chomping at the bit to get that thing in the water

and when the genset is providing ice cold air in the cabin :party-smiley-048:

The blowers in my boat fight against the air being sucked INTO the compartment by the engines when running since they blow air OUT of the compartment while at speed. I have noticed they get very warm and smell hot trying to fight against the flow of air. Tells me my compartment is ventilation-limited for motors. I do tend to leave them on frequently while idling or fresh off of plane to cut down on crankcase fumes from breathers.

I don't run them on plane, I don't want to suck any cool air off the bottom if there is any

I turn them on anytime when not on plane and engines are running. I crack the hatches when off plane, 600 SCI get cranky when hatch is left closed too long at idle.

It's 6.30 am here and I would normally be sound asleep but the boat was cleared through customs last night (after a small payment of 'tea money' was agreed upon) and is due at the marina around 8.00 am so I'm wide awake!

Good to read all the replies, a few good arguements on both sides. Think I'll alternate each day out, run with blowers on one day then blowers off the next......:)

RR

I have always been taught to turn those fans OFF when fueling so they won't spark the fumes. What say you?

I was always told to run them to evacuate the fumes before the saturation level could get high enough to ignite.
think about it. If there's fumes high enough to combust sitting over night for some reason. And you turn your blowers on to get the fumes out before starting. Why would it be a problem running them while refueling?

I can almost answer my own question......
On the dash of my 'new to me' boat, right near the blower switch, it says "Never run bilge blowers while on the plane" (or something like that) I'll check the exact wording tomorrow. It's factory Donzi printing so I'm happy to run with it.

RR

Plus there is a lot of draw on the system. My volt meter drops about .75 volts when turned on.
Best of luck with your new boat!

The Coast Guard suggest running the bilge blowers after filling up due to the chance of a blower actually pulling fumes into the bilge as gas fumes are vented out of the gas tank vent. As the tank is filled with fluid (gas), the air has to escape out of the vent. If the bilge blower is blowing air, it is also sucking air from somewhere, and if that somewhere is close to the gas tank vent, it could spell trouble.

Depending on all kinds of factors, gasoline needs to be somewhere in the 1.5% to 8% of volume by air to ignite. Under this it is too lean, over this it is too rich. A spark will not ignite if outside of those limits. Sucking in gas vapor through the bilge blower can get to that lower flammability index making for a bad situation. Once you are done filling up, the incoming gas is no longer pushing out a high amount of fumes under pressure, so the bilge blowers are good to go.

An example of being too rich would be if a boat fills up with gas, and for some reason or another several gallons of gas ends up in the bilge. The boater turns on the bilge blower, unties the boat and is on their way. The boat gets out a ways and "boom". What happened is that all of the gas in the bilge put the air over the upper flammability index, until the bilge blower (or the passive vents) replaced that rich air with clean air down to the point that the air/fuel mixture was in that window between the lower and upper flammability index. Any spark at that point could cause problems (another reason to only use sealed marine parts instead of car parts).

Anyway, thats my take on it..............

Keep in mind also that while the engine or engines are running they are essentially air pumps and are continuously pulling large volumes of air out of the engine compartment and exhausting them out the tail pipes. With out taking fuel that is atomized in the mixture into account and a volumetric efficiency loss in moving the air a 540 naturally aspirated CI engine at 2000 rpm should move approx. 312.5 CFM thus: 540 CI x 2000RMP/1728(cubic inches in a sq. ft.) / 2(intake charge per RPM)= 312.5 CFM A boosted application would result in > CFM numbers. Overall this does not take into consideration the boats ventilation set up IE: what is potentially moved in and vented out of the compartment via the engine compartment ventilation design. A twin engine boat would end up approx. doubling the volume. To answer the blower question: run them after fueling and before any start up IE: shut down period and always do a visual and sniff test first.

im no electrical engineer, but I thought that a circuit only sparks when connecting or disconnecting? And it's at the switch.

Could be wrong who knows.

I always opened the hatch and looked/sniffed around before I started the engines EVERY TIME (while running the blowers). Never on plane, there's so much air being exchanged while on plane I don't see how it could be a problem unless your tank is leaking...then you're in trouble regardless of the blowers.

Photo taken today, the dash on my little Donzi. You'd think Donzi would print their dash the right way up!

I fuel at land pumps miles away from the ramp where I launch, I therefore never use the blower. I open the hatch during the staring process and never smell fuel, engines are MPI. If I had carbs, I'd probably run them all the time, except on plane.

Keith

you have an australian phone but your north of the equator therefore all your pics will be upside down.
try flippin your phone around and the pics will be right side up

I like the way you're thinking but I have a Thai phone.......
:(