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Question about bilge blower vent lines-gctid465402

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  • Mileskb
    replied
    JimMc wrote:
    Your blower draws from the bilge to exhaust fumes. The manifold with the second line would very likely allow those fumes to be brought back into the bilge.

    Coast Guard regs say the intake and exhaust should be seperated by 18" to prevent drawing fumes back into the boat.

    I have blowers on both of the hoses on one side of the boat to exhaust fumes. The hoses on the other side of the bilge to allow fresh air in.

    I replaced the vinyl blower hose with Trident Polyduct. It is very tough compared to vinyl.

    I was thinking of adding a second blower as well... I din't think it would do any harm, but at the same time.. I'm not an engineer so hence my post here.

    Like yours the intake and exhaust are on opposite sides of the boat... but like you... I have TWO sets of hoses on each side. Seems short of Rick's install, a second blower might be worthwhile or at least couldn't hurt. The new ones are certainly quiet enough and cheap enough..

    I was more hoping to find out at some point how it looked originally, and grow from there.

    Leave a comment:


  • JimMc
    replied
    Your blower draws from the bilge to exhaust fumes. The manifold with the second line would very likely allow those fumes to be brought back into the bilge.

    Coast Guard regs say the intake and exhaust should be seperated by 18" to prevent drawing fumes back into the boat.

    I have blowers on both of the hoses on one side of the boat to exhaust fumes. The hoses on the other side of the bilge to allow fresh air in.

    I replaced the vinyl blower hose with Trident Polyduct. It is very tough compared to vinyl.


    Leave a comment:


  • 2850Bounty
    replied
    ishiboo wrote:
    Sounds about right... but do remember in addition to the 250CFM blower fan, you also have the engine sucking EXACTLY that 226cfm itself, and blowing it out the exhaust.

    [COLOR]"#0000FF" wrote:
    That was calculated @ 4k RPM. [/COLOR]

    The blower is simply for gasoline fumes, the engine has plenty of cooling and will suck in its own combustion air without issue.
    Correct! The vent louvers will generally supply more air than what engine demands are.

    Leave a comment:


  • Guest's Avatar
    Guest replied
    2850Bounty wrote:


    FWIW and FYI:

    The squirrel cage blower motor, on average, will exchange 250 CFM.

    Your 3.7L 470 engine @ 4k rpm, will require approx 226 cfm of combustion air.
    Sounds about right... but do remember in addition to the 250CFM blower fan, you also have the engine sucking EXACTLY that 226cfm itself, and blowing it out the exhaust.

    The blower is simply for gasoline fumes, the engine has plenty of cooling and will suck in its own combustion air without issue.

    Leave a comment:


  • 2850Bounty
    replied
    Mileskb wrote:


    I do have a hose that goes to the blower, but I really didn't know where it should point. I can aim it down low easy enough.
    Yes! Gasoline vapors will tend to lay low.

    Leave a comment:


  • Mileskb
    replied
    2850Bounty wrote:
    Miles.....

    While you are not moving, the blower motor will/should actually cause air to be pulled through three hoses, and exhaust through one.....
    That's what I wanted to know. If that's what it's supposed to do, then I'm all set as that's what it looks like it does.

    I do have a hose that goes to the blower, but I really didn't know where it should point. I can aim it down low easy enough.

    I do like your idea of all four intakes and adding a big honk'n blower to pull it all out. Very efficient.

    Leave a comment:


  • 2850Bounty
    replied
    Miles.....
    Mileskb wrote:
    Hello,

    I replaced my blower because it was making the i'm-old-replace-me noises.

    [COLOR]"#0000FF" wrote:
    Probably one of these????[/COLOR]



    [COLOR]"#0000FF" wrote:
    If you'd like quiet and longevity, http://"http://www.boat-heaters.com/...these.</b></u> [/COLOR]

    I was looking at my setup and got to wondering if it's actually set up the was it should be or did the PO make modifications/changes..

    How should the hose and blower be routed?

    I have TWO hoses on each side.

    [COLOR]"#0000FF" wrote:
    Typical. [/COLOR]

    The grills are correct as far as one side points forward, the other aft for intake and exhaust,

    [COLOR]"#0000FF" wrote:
    Typical. [/COLOR]

    but rather than the vents being like a manifold into one hose each side, there are two hoses on each side.

    [COLOR]"#0000FF" wrote:
    Again, typical.[/COLOR]

    The hoses are against the transom with one hose about mid-height to the engine and the other lower pointing toward the bilge. The blower is on the upper exhaust hose.

    [COLOR]"#0000FF" wrote:
    The blower motor may be attached to an upper vent hose, but there should be a second suction hose (attached to the blower motor) pulling from down low in the engine bay. [/COLOR]

    My question arose from seeing that it seems with this configuration the exhaust blower in the bilge would not only be pulling fresh air from the actual intakes on the other side of the bilge area [COLOR]"#0000FF" wrote:
    (that would be correct)[/COLOR], but also be pulling air from the other exhaust hose that is just a few inches away [COLOR]"#0000FF" wrote:
    (possibly while the blower motor is energized)[/COLOR] , potentially pulling fumes just exhausted back in from the other end [COLOR]"#0000FF" wrote:
    (I'd have say not if connected correctly). [/COLOR]

    This is the type of exhaust collectors I have on the sides of the boat of course covered with louvers pointing the correct way... but just wanted to show the "two hose" configuration.

    [COLOR]"#0000FF" wrote:
    Unless you are set up with a continous duty blower motor, one vent louver supplies two vent hoses as Incoming supply air.

    The other vent louver creates "pull" via one vent hose, and "forced" ventilation via the blower motor.

    [/COLOR]

    Rather than two hoses going to the bilge area should there be a Y connection or something,

    [COLOR]"#0000FF" wrote:
    I've never seen a Y used.

    These are air supplies, and can be randomly replaced.... perhaps one higher, perhaps one a bit lower. [/COLOR]

    or does the not-connected-to-exhaust-blower exhaust hose help with the circulation from the intake side of the compartment?

    [COLOR]"#0000FF" wrote:
    Not following you!

    One vent hose will be connected to the blower motor and will connect the blower motor to the plenum of the vent louver that faces AFT.

    The blower motor's "inlet" vent hose will pull air from within a "low point" of the engine bay. [/COLOR]
    Unfortunately I can't find a decent image to post for you.

    Basically you'll want the system to work while the boat is moving, and while the blower motor is not.

    If you have only two vent louvers, one will become air supply (louvers facing FWD), the other will become exhaust (louvers facing AFT).

    While you are not moving, the blower motor will/should actually cause air to be pulled through three hoses, and exhaust through one..... but when two hoses share a single plenum, things don't always go that way.

    Here's what I've done:

    I turned two vent louvers around to match the other two, making all four vent louvers now air intakes.

    I added two additional blower motor outlet shells, for my two continous duty squirrel cage blower motors at the transom.

    These two motors operate anytimg the engines are operating (plus prior to start-up).

    If the blower motors were turned off while under way, all four side louvers still act like intakes, and the transom mounted blower motors becomes passive.

    I'm not suggesting that this is for everyone..... just say'n.

    As long as the exhaust air is able to pull from down low, you should be OK.

    FWIW and FYI:

    The squirrel cage blower motor, on average, will exchange 250 CFM.

    Your 3.7L 470 engine @ 4k rpm, will require approx 226 cfm of combustion air.

    .

    Leave a comment:


  • Mileskb
    replied
    Nehalennia wrote:
    Your theory sounds right that you may be pulling the exhausting fumes back in but with it mixing at the surface, I suspect it will be minimal.
    I was thinking I would get better "flow" by not having that 2nd exhaust hose where all air would be pulled in from the intake side and all exhaust air out the exhaust side, but really just curious what the "correct" way is. I have no way of knowing how the boat came from the factory and was hoping someone else had a late 1970's boat they knew was stock to shed some light...

    Leave a comment:


  • Guest's Avatar
    Guest replied
    Your theory sounds right that you may be pulling the exhausting fumes back in but with it mixing at the surface, I suspect it will be minimal. I have 4 vent hoses. Two starboard, (shown) that provide ventilation unassisted. Then two on the port side which one of them has the blower attached. One is higher than the other on both sides.


    Leave a comment:


  • Mileskb
    started a topic Question about bilge blower vent lines-gctid465402

    Question about bilge blower vent lines-gctid465402

    Hello,Not a critical issue (maybe).. I replaced my blower because it was making the i'm-old-replace-me noises. I was looking at my setup and got to wondering if it's actually set up the was it should be or did the PO make modifications/changes..How should the hose and blower be routed?I have TWO hoses on each side. The grills are correct as far as one side points forward, the other aft for intake and exhaust, but rather than the vents being like a manifold into one hose each side, there are two hoses on each side.The hoses are against the transom with one hose about mid-height to the engine and the other lower pointing toward the bilge. The blower is on the upper exhaust hose.My question arose from seeing that it seems with this configuration the exhaust blower in the bilge would not only be pulling fresh air from the actual intakes on the other side of the bilge area, but also be pulling air from the other exhaust hose that is just a few inches away, potentially pulling fumes just exhausted back in from the other end.This is the type of exhaust collectors I have on the sides of the boat of course covered with louvers pointing the correct way... but just wanted to show the "two hose" configuration.

    [img]/media/kunena/attachments/vb/769901=36440-!B9Bi2)!!Wk~$(KGrHqN,!iMEzN9OnYO(BM4pb01OKw~~0_12. JPG[/img]Rather than two hoses going to the bilge area should there be a Y connection or something, or does the not-connected-to-exhaust-blower exhaust hose help with the circulation from the intake side of the compartment?Thanks....
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