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  1. #1
    Join Date
    Aug 2017
    Location
    southern California
    Posts
    97

    Default what is this in the exhaust stream?

    This is my starboard motor at start up. It clears completely after about 10 minutes warm. It smells gassy but does not leave a slick. Oil looks good on dipstick. My starboard carb needs attention. I notice that the secondary plates are dry at idle but when engine shuts down, fuel seeps onto the throttle plates from somewhere. Im kinda thinking that raw fuel is puddling into the intake after shutdown, and perhaps the cloudy emission is fuel mixed with water, but weird it doesnt slick.
    Last edited by realcaptron; 12-05-2017 at 07:10 PM.

  2. #2

    Default Re: what is this in the exhaust stream?

    I think your probably onto the the right track. Sounds like something like a needle or a bit of crud is keeping something open that shouldn't be at shutdown. I had a similar smell on my carbs, but I rebuilt them, and then zeroed them in with a vacuum gauge, and they work great now. Rebuilding is for the most part (after reading how) really pretty simple.

    Good luck.
    Duke1

  3. #3
    Join Date
    Dec 2006
    Location
    Chaumont Bay, N.y., USA
    Posts
    5,373

    Default Re: what is this in the exhaust stream?

    Ayuh,.... If the carb needs a rebuild, it's highly likely it's dumpin' raw gas into the exhaust stream,....
    Any Grease is Better,... Than No grease at All....

  4. #4
    Join Date
    Dec 2008
    Location
    Bourne, MA, USA
    Posts
    315

    Default Re: what is this in the exhaust stream?

    Could it be there is gas flowing through the tygon tubing, if so equipped, from the fuel pump to the base of the carb?

  5. #5
    Join Date
    Sep 2008
    Location
    Maryland - USA
    Posts
    6,970

    Default Re: what is this in the exhaust stream?

    I'm pretty sure he's got aftermarket Holleys.....so the tygon tube would likely go to a hose barb on the flame arrester.....though the newer 4160 appears to have the tygon hose barb into a primary primar bore, like the quadrajets have.....

  6. #6
    Join Date
    Aug 2017
    Location
    southern California
    Posts
    97

    Default Re: what is this in the exhaust stream?

    Not sure what a tygon tube is but the starboard carb has tube from fuel pump to arrest or as Mark describes. Port tube going to base of carb.

  7. #7
    Join Date
    Sep 2008
    Location
    Maryland - USA
    Posts
    6,970

    Default Re: what is this in the exhaust stream?

    the plastic tube running from the fuel pump to the carb is usually made from TYGON...its known as the sight tube....its purpose is twofold: 1)to provide a visual indication when the fuel pump diaphragm has ruptured & 2) to route any fuel the seeps past that diaphragm into the carb.

    The sight tube should enter the carb above the throttle plates so I'd suggest investigating the port install when you can...and fixing it...

  8. #8
    Join Date
    Aug 2017
    Location
    southern California
    Posts
    97

    Default Re: what is this in the exhaust stream?

    , Mark I am voice typing here so we'll see how the spelling turns out. I will check out these tubes more thoroughly on my next visit to the boat however on the starboard side the two of I am referring to is actually a clear plastic hose that is basically runs from the fuel pump to the outside of the arrester and sort of just hanging by their restaurant like a breather hose. The Portside I will take another look at but I don't believe it is clear and it seems to enter at the base of the carburetor almost like into a carburetor vacuum port

  9. #9
    Join Date
    Aug 2017
    Location
    southern California
    Posts
    97

    Default Re: what is this in the exhaust stream?

    Mark, I have a clear plastic hose running from fuel pump to outside if arrestor like a breather. That is starboard. Port side has No Tube or hose between fuel pump and carb.

  10. #10
    Join Date
    Sep 2008
    Location
    Maryland - USA
    Posts
    6,970

    Default Re: what is this in the exhaust stream?

    if it is clear (vs yellow tint), its not tygon.....better make sure what ever is there will tolerate the fuel you use....

    and there should be a tube from the port side pump....does the pump have the hose barb fitting on it? if not, I'd be inclined to get a marine rated pump on that side .....

  11. #11
    Join Date
    Aug 2017
    Location
    southern California
    Posts
    97

    Default Re: what is this in the exhaust stream?

    Quote Originally Posted by makomark View Post
    if it is clear (vs yellow tint), its not tygon.....better make sure what ever is there will tolerate the fuel you use....

    and there should be a tube from the port side pump....does the pump have the hose barb fitting on it? if not, I'd be inclined to get a marine rated pump on that side .....
    yikes....mow I have more to learn about this old boat. I've owned at least 20 boats in my life and I have never paid attention to this. I will try to attach a pic of my starboard side carb with the clear hose outside of arrestor to fuel pump. I see no purpose for this. The port side fuel pump does not have a fitting on it that I can see to go to carb.

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