If the engine doesn't start, it drowns?

Discussion in 'Inboards' started by CaptainAB, May 8, 2010.

  1. apex1

    apex1 Guest

    Does´nt a 4 stroke engine pump it´s displacement with every second turn? So, a 4 litre 4 cyl, will pump 20 litre with 10 rotations?;)
     
  2. Frosty

    Frosty Previous Member

    How can you pump water with air? I think air floats does'nt it, so it just pushes past and to the surface.

    Gonzo is correct if you crank enough you will fill the exhaust system.

    You should have -- a drain if you are in such difficult circumstances.
     
  3. mark775

    mark775 Guest

    No, a drain is only for winterizing. A slow, dying-battery crank will not forcefully push water uphill (the exit of the waterlift will remain full). Also, you are forgetting an active bypass on the uphill water flow before it goes over the top (before it is injected into the exhaust). This allows cranking without flooding the exit of the lift muffler, gives a great visual reference that you have waterflow, and adds a layer of safety to the system.
    More water is used for engine cooling than is needed for exhaust cooling, so bypass about 1/3 of the water that leaves the engine and send it over the side of the boat and you'll easily reduce back pressure by 1" Hg or more (water plus heat makes steam at some multiple of the volume of the individual components) and alleviate the drowned engine possiblity. It is very simple and the WAY IT SHUD BE DONE WITH A WATERLIFT. I don't want to hear any talk of cranking a bit, draining, installing heat lamps in your exhaust system, chemical dessicants, or any other goofy ideas one may come up with. PUT AN F'ING BYPASS!
     
  4. gonzo
    Joined: Aug 2002
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    gonzo Senior Member

    If you don't want to hear cover your ears. All manuals specify that if the engine does not start after cranking for a while the muffler should be drained.
     
  5. capt littlelegs
    Joined: Apr 2010
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    capt littlelegs New Member

    Not all, what if you don't have a muffler?
     
  6. tunnels

    tunnels Previous Member

    That Vetus diagram is the worst of the bad installations i have seem yet:eek: . The water lock muffler behind the motor needs as low as possible and to have a minimum of 6 times the capacity of the pipe from the muffler to the back of the hull where it goes out the back . The vertical pipe going out needs to be the diameter of the pipe off the bottom of the the muffler body !. the outlet pipe from the muffler need to rise up as high as possible then have a steady constant fall all the way to the back where it exits .
    Over the past 25 years this is the simple principle i have always used and have never ever had the hint of a problem be it a power boat from 10 hp through to 300 hp or a Yacht used for cruising or racing . I always make my own glass pipes as well as the mufffles , all made from fibreglass and Vinylester resins:D
     
  7. mark775

    mark775 Guest

    I don't have time to read it all but the first sentence of tunnel's - correct. Gonzo Googles more **** and puts forth more idiotic responses than any ten others. Ask him for advice on punishing a ferro treasure and nothing more as he really knows next to nothing not found on the net solely to impress himself. ...Attaboy, Gonzo - you were able to look at sales crap from Vetus! Somebody give him a cookie!
     
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  8. powerabout
    Joined: Nov 2007
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    powerabout Senior Member

    Nice but not legal in anybodys rules as its not fireproof
    You need to use phenolic resins with fire ratings
     
  9. CDK
    Joined: Aug 2007
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    CDK retired engineer

    In my boat I did it like this.
    The gray parts are hoses, the muffler I welded from stainless steel.
    In the exhaust hose the airspeed is more than sufficient to expel the modest amount of water injected in the turbo charger housing through a 1/4" nozzle.
     

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  10. murdomack
    Joined: Jun 2007
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    murdomack New Member

    You can do amazing things with 12v equipment. Just be carefull that the material will not corrode, most gardening valves will be cheap and cheerful I imagine. What you could try is attaching a 12v linear (or maybe rotary) actuator to a marine-quality ball valve.

    I've just installed one of these clutched hydraulic pumps. I get enough pressure at idle revs to work my proposed thruster (I haven't bought it yet as I wanted to test my system against the relief valve before committing), but my revs are slowed a bit which might mean I dont get the required flow.
    It might speed up once running through the motor instead of the relief valve, but if it doesn't I am toying with the idea of using a small 12v linear actuator wired to the thruster joystick to push the throttle lever enough to overcome my rev drop.
     
  11. Brent Swain
    Joined: Mar 2002
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    Brent Swain Member

    On Metalboatsociety.org a Port Townsend diesel mechanic was quoted as saying "If everyone went for dry exhausts and keel cooling , us mechanics would all be out of work.' The big screwup here is putting water into your exhaust pipe. Last time I was in Tonga I met a couple who had lost 2 engines in 4 years from condensation on the valves from wet exhaust. They went for dry exhaust as soon as they got home. Another friend recently seized his engine from the same cause.
    Commercial boat operators can only laugh at yachties being so dense as to pump water into their exhausts
     
  12. CDK
    Joined: Aug 2007
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    Location: Adriatic sea

    CDK retired engineer

    To say this politely, these are very, very biased opinions.
    My estimate is that 98% of all marine engines on this planet have a wet exhaust. The concept of an engine failure due to condensation on the valves doesn't make sense to me. Condensation takes place on all cold surfaces when water vapor is present and is the only reason car mufflers have a limited service life.

    All combustion engines produce large amounts of water vapor that condensates as soon as the metal parts cool down to the dew point, no matter what type of exhaust system is employed, but vital parts are protected by their oil film. Only when left out of service for months without proper care, damage can be caused because of rusted valve stems or piston rings, mainly in gasoline engines.
     
  13. murdomack
    Joined: Jun 2007
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    murdomack New Member

    Well, it's probably easier for commercial boats to have dry exhaust set-ups, same with canal narrow-boats etc.

    Yachts are restricted in how they run their exhausts, whether due to sails, in the case of vertical runs, or cabin/locker arrangements when running through the hull. I agree that if it is feasible keel cooling is the better set-up, but it is seldom so in most boats.
     
  14. apex1

    apex1 Guest

    That was really very polite, because the statement was bare nonsense.....:mad:

    You are right on the condensation issue.

    The dry stack vs. wet exhaust is a discussion as old as marine engines. And it will remain, because both systems have their advantages.
    Even a mixed system is not uncommon (dry stack and wet manifold) on many fishing boats.

    But Brent is a fully digital man, either 1 or 0, all or nothing, black or white. He does not know that "boating" is the translation of "compromise".

    Regards
    Richard
     

  15. powerabout
    Joined: Nov 2007
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    powerabout Senior Member

    I guess its just that if you have a wet exhaust you need to use your boat every day or have a dry one.
    Funny how the reality is the opposite
    Commercial dry and recreational wet?
     
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