Announcement

Collapse
No announcement yet.

Carburetor freezing is that normal-gctid361831

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

    Carburetor freezing is that normal-gctid361831

    I have a 7.4L with a webber carb. It's freezing up when I first start it. I have to let it sit for about 5-10 minutes after i warm it up so it thwas out and after it runs great. Is that normal at this time of year? I live in Coquitlam BC Canada. Oh and I just had the carb rebuilt and set up.

    #2
    I'm just curious, at what temperature are you boating when carb frezez? I have heard airplane carbs freezing, that's why they install carb heater.

    Comment


      #3
      Did this happen before the rebuild? I've never had this experience.

      Comment


        #4
        It's freezing between 32 to 60F. It was doing it before the rebuild as well. The mechanics say its normal but freinds that have boats say it doesn't sound right. It sucks the air in so fast that it freezes and when the engine compartment warm up it's fine. But I have to let it sit when it warm up so the frost melts. You can actually see it.

        Comment


          #5
          Just asking: could there possibly be a hose/tube connection missing? Does your flame arrestor have hose connections from the valve covers? It's got to get some heat from somewhere - freezing when the temp is 60 degrees is definitely not normal.
          Two C's 1990 3888 MY, 175 Hinos, Hurth 630 Trannys
          Past Commodore Emerald Rose Yacht Club
          Member International Order of the Blue Gavel
          MMSI: 338030604

          Comment


            #6
            Old chevys used to have a fabric/ceramic tube that went from the top of the exhaust manifold to the air cleaner. It was to combat this very thing. Yes with out a way to heat the air it can freeze.

            Most boat manufacturers don't expect you to use it during near freezing temps so they haven't made a way to Heat it.
            1989 Avanti 3450 Sunbridge
            twin 454's
            MV Mar-Y-Sol
            1979 Bayliner Conquest 3150 hardtop ocean express.
            Twin chevy 350's inboard
            Ben- Jamin
            spokane Washington

            Comment


              #7
              If it's also running rough when cold, it's possible you have a stuck float that is allowing excess fuel to leak onto the throttle plates.

              A couple whacks might be all it takes. A properly set up carb shouldn't have icing problems on a 4 stroke boat engine.
              Doug
              Hanging Loose
              98 Carver 350 Mariner
              2013-
              KRUSTY KRAB
              2001 305
              5.7 BII
              2006-2013

              Comment


                #8
                carb icing is way common on motorcycles. Most often in temps above freezing when its moist out. I've rigged all sorts of stuff to act as a fix. If you have some flex tubing that you can use to form something like the older cars had: a tube running from just on top of the exhaust manifold to an outlet right next to the carb body, or into the flame arrestor, that should work. You'll need to block it off or move it for normal running so it will be kind of a pain, but at least its a solution. It really doesn't take too much.

                Comment


                  #9
                  Boat engines with carbs are supposed to have the valve cover hose to the carb.

                  Both valve covers !!!!! If your engine does not have them then whats on top ?

                  Should be a spark arrestor.
                  Be good, be happy, for tomorrow is promised to no man !

                  1994 2452, 5.0l, Alpha gen. 2 drive. Sold ! Sold ! Sold !

                  '86 / 19' Citation cuddy, Merc. 3.0L / 140 hp 86' , stringer drive. Sold ! Sold ! Sold !

                  Manalapan N.J

                  Comment


                    #10
                    Could it be that this has been misdiagnosed, and you are seeing icing or sweating externally, and the engine is simply too cold to atomize the fuel correctly?

                    Otherwise, how would vehicles in Alaska, Canada and/or up state areas fire up if actual fuel icing was to occur?

                    Icing up is nothing more than a form of the refrigeration principle that relies on rapid expansion of gasses from a higher pressure (in this case "ambient pressure") into a lower pressure area. Results: reduced temperature.

                    The icing requires moisture since air and/or fuel alone will not freeze at these temperatures.

                    Just a thought!

                    .
                    Rick E. Gresham, Oregon
                    2850 Bounty Sedan Flybridge model
                    Twin 280 HP 5.7's w/ Closed Cooling
                    Volvo Penta DuoProp Drives
                    Kohler 4 CZ Gen Set

                    Comment


                      #11
                      I'm not familiar with your Weber carb. Some carb designs are more prone to icing than others. To combat carb ice, most engines have some way of routing exhaust gas near the carb base. Most V8s have a passage in the intake manifold that routes the gas from bank to bank. In automotive applications a thermostatically controlled heat riser valve in the exhaust system ensure flow when cold. Marine manifolds don't have this provision so flow will be less. It's also possible that this passage may be blocked or severely restricted in your engine.

                      I'm guessing that you are experiencing icing for several reasons. It may have something to do with the carb design, it may have something to do with the heat riser passage. It may have a lot to do with the fact that your engine space is probably filled with relatively cold and very damp air. With the water cooled exhaust manifolds it's pretty hard to have an "instant" heat source for the incoming air, like the "stoves" on an automotive manifold so you are limited in what kind of "fixes" you may have at your disposal.

                      The more air flow you have when the engine is cold and the air is damp, the more prone it will be to icing. If possible, try warming up the engine at the lowest speed it will idle smoothly. If you have shore power on the boat, just a small heat source in the engine space will help a lot with air quality, and everything in that space will love you for it.

                      Comment


                        #12
                        The exhaust heat cross-over needs a few minutes to produce heat to the lower section of the intake manifold.

                        Robert, if this is indeed an otherwise un-curable cold/moist air situation, I wonder if an electric pre-heat unit of some sort could be incorporated... similar to what diesel engines use.
                        Rick E. Gresham, Oregon
                        2850 Bounty Sedan Flybridge model
                        Twin 280 HP 5.7's w/ Closed Cooling
                        Volvo Penta DuoProp Drives
                        Kohler 4 CZ Gen Set

                        Comment


                          #13
                          Used to own a uniflite with twin Chrysler 318's. They would ice up on cold start up after 3 minutes, if ambient temp was less than 40-45F and raining or foggy conditions. Then stall from over rich conditions, just like a stuck choke. Solved the problem by heating the carbs fuel bowel end with hair dryer for 5 min before startup. Later i installed block heaters & plugged them in for 1 or 2 hours before start up. Engines loved block heaters!

                          If on the hook would start engine as soon as detecting it choking shut it off and wait for couple minutes... Two or three of this routines warms the carbs up enough to prevent icing...
                          Rod
                          1991 4387
                          Sidney, BC

                          Comment


                            #14
                            Thanks guy's, I love the block heater idea. There are hoses coming from the valve covers to the arrestor but they just clip onto this piece of metal so I don't think any of the heat coming from them are getting into the carb. I thought of putting a heater down in the engine compartment too. The air is very damp up here and my brother that is a chevy mechanic says it's quite common. I am going to look into a block heater I like that idea. The carb was set up by a mechanic so I could only assume that everything is correct.

                            Comment


                              #15
                              You have to be careful enclosed area with a spark can mean doom. I always open up the doghouse and air out the engine before starting, i usually jump on the boat before launching at the dock by the time i park the truck and trailer and get back to the boat it's at least five minutes.

                              If there is a line at the dock then even longer. I start the engine and look for leaks every time, the engine has to warm up anyway.

                              Rick had a solution they do make fuel warmers used on diesels.
                              Be good, be happy, for tomorrow is promised to no man !

                              1994 2452, 5.0l, Alpha gen. 2 drive. Sold ! Sold ! Sold !

                              '86 / 19' Citation cuddy, Merc. 3.0L / 140 hp 86' , stringer drive. Sold ! Sold ! Sold !

                              Manalapan N.J

                              Comment

                              Working...
                              X