explanantion/education needed

Can someone explain the component of the bilge blower/ventilation system.

I have an 1986 Wellcraft Excell 200 with a Merc 260/Alpha 1. I totally understand the logic and theory behind the system.

What are the components? So fresh air is pumped in to replace the potentially gas vapor filled air that is being pumped out by the blower to prevent a spark ignited fumes and causing a fire/explosion.

Where is the intake for this air and the exhaust for this pump?

I am very familiar with outboard bass boats, but I recently bought this I/O runabout for the family and have learned A TON on this website. Thanks to you all I have successfully resolved wiring issues with nav lights and my bilge pump. Learned lots about handling my boat from lots and lots of reading.

I am not close to my boat so I have to read read read and then look, inspect, and figure it out when I am at the lake house.

Thanks for any input you have.

Re: explanantion/education needed

There are 4 components to your blower system.

At least 2 vents

1 hose

1 blower

The vents that do not have a hose on them are the INTAKE vents. One vent will have a hose that connects to the blower. That is the EXHAUST vent.

The system works when the blower (which MUST BE spark protected) starts blowing bilge gases out of the EXHAUST vent. This lowers the pressure in the engine compartment. This lower pressure pulls fresh air into the engine compartment through the INTAKE vents.

The above is why you DO NOT run your bilge blower when fueling your boat. It could pull gas fumes from the fueling area into the engine compartment through the INTAKE vents and cause an explosion when you start your boat.

Re: explanantion/education needed

45 is correct on how the system works. The vents are most likely located on the hullsides aft just below the rubrail. It is important that the exhaust hose be placed low in the bilge as gas fumes are heavier than air and will collect in the lowest parts. It is also IMPERATIVE that you run your blower for several minutes before you start your engine each and every time! Down here in Florida, too many boats simply blow up because operators don't heed this warning!

Re: explanantion/education needed

As mentioned above the exhaust hose should be mounted low and should exhaust on the opposite side of the boat from the intake. Intake should be mid height on the opposite side of the hull. This will ensure you don't get a short circuiting of the gas fumes

Re: explanantion/education needed

OK, makes sense, I know where the vents are at, just little plastic grills that cover up hole on each side of the hull towards the stern. The intake is right next to my bilge pump outlet

I will check the placement of the hoses, do those extend up under the floor towards the bow or the region near the console?

Also, I notice that my blower sounds different after running for about 30 or 40 seconds, it 'whines' at different pitch. I assume that the blower has enough umph that I can feel the air being blown out?

I use the blower each time, just wanting a better understanding of what it up and how it works.

Re: explanantion/education needed

It is my assumption that the vent that is right above the red, white, and blue Wellcraft emblem is the intake. The blower and apparent exhaust line is on the opposite side.

I added a few extra pics just to show off my new to me boat.

Re: explanantion/education needed

Bingo.

As for the sound of the blower changing: I'd want it to sound the same the whole time. The motor might be on its way out, and it might not be spinning/pumping as it should from the moment you turn it on.

Run and feel it early and often until you know whether it is doing its job.

Re: explanantion/education needed

hawghead said:

OK, makes sense, I know where the vents are at, just little plastic grills that cover up hole on each side of the hull towards the stern. The intake is right next to my bilge pump outlet

I will check the placement of the hoses, do those extend up under the floor towards the bow or the region near the console?

Also, I notice that my blower sounds different after running for about 30 or 40 seconds, it 'whines' at different pitch. I assume that the blower has enough umph that I can feel the air being blown out?

I use the blower each time, just wanting a better understanding of what it up and how it works.

Click to expand...

Yep, those are the vents, and no, the hoses should just run down toward the bilge of the engine. I have two, one runs to the front of the engine, one to the rear. They are only sucking air out of the engine compartment, where the fumes would have the most chance of being near a spark (at least I have never heard of any running to the bow or console!).

If after the blower runs for 30-40 seconds it changes sound...is that like it sounds like its trying to suck more air but it cant??

That makes it sound like the intake vents are clogged or closed or something (not getting enough air). And it would probably take about 30 seconds or so before the pump pulled enough air to make the high pitch sound...

I would check the intake vents, as that could also negatively affect the naturally aspirated engine (limiting air flow for the intake...possibly).

If you have two "tubes" running in the engine, you would need at least 3 vents (two exhaust, one intake) I have two of each. As someone mentioned earlier, you can have just one exhaust and one intake. Just ensure that the intake is free to allow air to flow.

Re: explanantion/education needed

OK...

I got it, the blower only vents the engine compartment since that is the area where the greatest risk of "unwanted ignition" exists. Cool.

I will certainly check the vents and lines to ensure no clogs exist and that I can still feel air flowing the entire time the blower is blowing. Thanks folks.

Re: explanantion/education needed

would it be safe to just lift the engine cover for a minute and then start it with out running the blower?Then close the cover after its started.

Re: explanantion/education needed

karatejoe said:

would it be safe to just lift the engine cover for a minute and then start it with out running the blower?Then close the cover after its started.

Click to expand...

Gas fumes are heavy, they go to the bottom, bilge, they have to be pumped out, opening the engine cover won't help, now after running the blower you can lift the cover and sniff to see if you smell gas before you start the engine.

Re: explanantion/education needed

I agree with all of the posts to a certain extent. There are a few other things concerning bilge venting I'd like to add:

The sniff test - while running the blower, take a second and open the doghouse. Take a sniff for fumes. This does 2 things. One, it will alert you for gas fumes as the human nose can detect as little as 10 parts per million of gasoline vapor. Two, it opens up the area, making any gasoline fume-rich enviroment too lean for combustion.

Idle - a lot of carbed engines tend to not be tuned too well and spill over fuel when brought down to an idle. I always run the blower when at an idle, even im my MPI boat. Good habit to have. Besides, it's brings cooler, fresh air into the doghouse while moving slow.