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1987 2550 5.7 OMC stumbles and dies over half throttle-gctid398298

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    1987 2550 5.7 OMC stumbles and dies over half throttle-gctid398298

    Hi every one, this is my first post but I have been lurking in the shadows for years. I got "About Time" out on the water for the first time this season a few weeks ago and she ran great all day. Then after stopping to watch seals sunbathing on rocks when I opened up the throttle beyond about half she stumbled and quit. I started it back up and the same thing happened again only this time it didn't quit because I throttled back and made our way back to the dock...slowly. I changed the fuel filter and took her back out and she ran great all day again... for a while. Then the same thing happened again. So my question is do I just have 100 gallons of bad fuel or could it be an problem in the ignition system? Is there a way of improving the gas quality or do I need to dispose of it and start fresh. I have burned about 90 gallons so far this year and topped off with fresh fuel each time. I did put it away with an extra healthy dose of marine stablizer in the tank 2 seasons ago. Any thoughts on my issue is greatly appreciated!

    #2
    how mucky was the fuel in the filter?

    Comment


      #3
      I dumped the fuel from the filter into a clean glass jar when I changed it in hopes of seeing a puddle of water form in the bottom but there was no visible water present. I then went on to hope that the water "must be stuck in the paper of the filter". The fuel looked fine with the exception of a few small specks of dirt or whatever that ended up in the jar. The fuel smelled a little "stale", but as I stated, the boat ran fine all day.

      Comment


        #4
        sure sounds like a fuel issue, but looking down the carb while it acts up will verify that fuel is leaning out.

        checking fuel pressure at the carb inlet always a good test - should be around 4-8 psi -test needs to be done under load- verifies fuel pump and supply

        is the flame arrester nice and clean?

        I'd probably zip the spark plugs out looking for evidence of lean/rich or water on them and do a compression test for the 10 minutes it takes

        while they're out.

        then, I'd move on to the anti siphon valve and tank venting to make sure no restrictions for fuel to get out of the tank

        you have burned 90 gallons - so you put 90 gallons of clean fuel - how big is the tank? I can't imagine it has much stale fuel at this point.

        Comment


          #5
          Thanks for your response and for the ideas.

          I had already pulled out one spark plug and it looked good to me. Slightly tanned, dry and the electrodes were not at all worn looking. I have no problem with pulling them all and doing a compression check, but compression problems don't come and go. Or do they?

          An additional piece of information that made me question the possibility of an ignition problem is that the last time it happened I could actually smell raw fuel so bad that I actually shut the engine down and looked for a leak, but there was none. The fuel smell must have been coming either from the intake or exhaust.

          The flame arrestor is clean, and again, I am trying to understand how a constant problem like a dirty flame arrestor would that cause an intermittent problem?

          I am unfamiliar with the anti siphon valve. Is that on the fuel line or is it part of the vent?

          I definitly agree that checking fuel pressure would answer some questions, but why does it have to be done under load? I am not questioning your advice, I am just trying to learn. The issue for me is that I trailer my boat and it is a bit of an undertaking to get the boat in the water in order to put the engine under load. The tank is 100 gallons so I have burned nearly the capacity of the tank but I am concerned that I added fresh gas to contaminated fuel twice and that the fuel is still contaminated, but as i mentioned, it looked fine.

          My ignition is points and condenser. Do you think a bad condenser would cause these symptoms?

          Comment


            #6
            Could be the coil. I had a car do weird things once. It would go all day and then all of a sudden, no go.
            David
            1999 Bayliner 1750 Capri. 3l Mercruiser Alpha

            2014 Yamaha VX Cruiser

            Comment


              #7
              I was having same problem with our new to us 2452. Dealer change all obvious electrical and fuel parts, also I complete carb rebuild. After alot of head bounding, they ran engine on a seperate 6 gal. tank. Boat ran like a scared rabbit. Found out the fuel feed line from the tank was collapsing above 3000 RPM. Just the inner lining so you could not see it happening. Hope this might help you.
              1994 2452
              5.7L Alpha Gen. II
              "HOOK EM"
              :Sterling Heights, MI
              MMSI#338128565

              Comment


                #8
                Davidlyne wrote:
                Could be the coil. I had a car do weird things once. It would go all day and then all of a sudden, no go.
                someone has as their signature line "when everything points to fuel system, go for ignition"

                That's why I started with looking down the carb. and checking fuel pressure to the carb under load.

                until a few tests are done, fuel and ignition symptoms are similar unfortunately.

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