why no Carb Icing on boats (or cars) only aircraft?

Discussion in 'Gas Engines' started by Squidly-Diddly, Nov 4, 2018.

  1. Squidly-Diddly
    Joined: Sep 2007
    Posts: 1,280
    Likes: 31, Points: 48, Legacy Rep: 304
    Location: SF bay

    Squidly-Diddly Senior Member



    about 3:38:00 mark.

    Says mostly happens at 80+% humidity and under 70'F.
    Says remedy is to throw "Carb Heat" switch for warm air to carb.

    I'm thinking 80+/70- is a lot of boating, and unlike cars many boats run close to max power most of the time. Many cars/trucks have intake hoses that tap fresh cold air at grill instead of semi-heated air from under hood. Never heard of a car getting Carb Icing even at 100%/40'F.

    Cars (used to) get "vapor lock" if fuel line gets too hot and fuel vaporizes and blocks flow.

    This about light planes that do most of their flying below the elevation of many lakes.

    What gives? Are light-plane carbs fundamentally different from their surface-borne counterparts?
     
  2. Mr Efficiency
    Joined: Oct 2010
    Posts: 6,772
    Likes: 178, Points: 63, Legacy Rep: 702
    Location: Australia

    Mr Efficiency Senior Member

    And temperature does decrease steadily with increase in altitude.
     
  3. Blueknarr
    Joined: Aug 2017
    Posts: 333
    Likes: 32, Points: 28
    Location: Colorado

    Blueknarr Senior Member

    The consequence of an automotive or marine carburetor freezing up are far less dire than an airplane's.

    Airplanes have extra failsafes because they can never be parked on the shoulder or let drift for even a moment.
     
  4. Barry
    Joined: Mar 2002
    Posts: 983
    Likes: 48, Points: 28, Legacy Rep: 158

    Barry Senior Member

    attached an interesting video of an explanation
     
  5. gonzo
    Joined: Aug 2002
    Posts: 13,079
    Likes: 291, Points: 93, Legacy Rep: 2031
    Location: Milwaukee, WI

    gonzo Senior Member

    Car carburetors ice up too. That is why there is a stove connected to the air filter intake.
     
  6. Barry
    Joined: Mar 2002
    Posts: 983
    Likes: 48, Points: 28, Legacy Rep: 158

    Barry Senior Member

    Not sure what you meant by "stove"

    The hose coming from the top of the valve cover to the air intake is the PCV hose (positive crankcase ventilation) that takes any fumes created in the engine body itself and runs it back through the intake so the fumes do not reach the atmosphere or the engine compartment. These fumes would be created by "blowback" gases leaking past rings or even just hot oil fumes.

    There may be, (so many hoses on the new emissions engines to figure out) another source of hotter air controlled by the EGR valve, Exhaust Gas Recirculation that takes a portion of the
    exhaust gases and returns some of it back to the intake to help in reducing nitrous oxygen from the emissions.

    While the warmer recirculated gases may reduce the chance of automobile engine carb icing, I wonder how important that this function is. With the new EFI engines, there would not be the cooling effect from the evaporating gasoline as it changes from liquid to vapor which I thought was one of the reasons for carb icing at low intake air temperature conditions
     
  7. ondarvr
    Joined: Dec 2005
    Posts: 1,778
    Likes: 83, Points: 48, Legacy Rep: 506
    Location: Monroe WA

    ondarvr Senior Member

    There is a ducting system that pulls warm air off the outside of the exhaust manifold on old carbed cars.

    I’ve had carbs on just about every type of application freeze up at one time or another in cold weather.
     
    Last edited: Nov 6, 2018

  8. gonzo
    Joined: Aug 2002
    Posts: 13,079
    Likes: 291, Points: 93, Legacy Rep: 2031
    Location: Milwaukee, WI

    gonzo Senior Member

    The sheet metal cover over the manifold is commonly called "stove".
     
Loading...
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.