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Blackmax 200 spraying fuel

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  • Blackmax 200 spraying fuel

    I was doing a compression test this weekend as I am trying to determine why I am not reaching max WOT. I recently downsized my prop with very little impact - see the post in the prop section. Anyway, I had the cowl off the engine warming it up and noticed it was spraying fuel from what I assume would be the gasket between the carbs and manifold. Right onto the starter and other electricals. Awesome. Very quickly shut down and dried everything before doing my compression test.

    I did not have a wrench to access the bolt around which it seemed to be leaking around. This was the only spot it seemed to be leaking from. So, do you think I am going to need a new gasket? Just a loose bolt? Could this be causing my lack of top end? Compression tested 100-110 across all six with a warm engine. Not sure if that is good or just passable with a warm engine.

    I also found my idle issue. It liked to stall after a couple of minutes of idling and ran very rough. The exhaust bypass was stuck against the inside of the cowl and not allowing the exhaust to exit as it should. With that straightened out and the cowl off it ran just fine. I'm assuming it was a combination of too much backpressure and the intakes sucking in exhaust.
    DSiekman
    2000 Cobalt 293 Twin Volvo 5.0 Gi DP - Sold
    1978 (or 79?) Hydra-Sports 21' CC with 200 Black Max
    2001 F250 7.3 Powerstroke (With a few goodies)

  • #2
    The intake leak is likely to affect performance at low speed. It could affect high speed performance as well, but this is more rare. I would replace the carb base gasket, as they are cheap and it will save time.

    Comment


    • #3
      The idle is a little rough. I'm debating how much effort to put into this motor as I'm supposed to have a 4 stroke rebuilt this winter - the boat isn't worth a new motor. Obviously I have to fix the fuel issue before I can use it again but I'm not sure it is worth much more effort...unless the rebuild doesn't work out
      DSiekman
      2000 Cobalt 293 Twin Volvo 5.0 Gi DP - Sold
      1978 (or 79?) Hydra-Sports 21' CC with 200 Black Max
      2001 F250 7.3 Powerstroke (With a few goodies)

      Comment


      • #4
        I watched the video in slow motion on a larger screen. It appears as though the fuel is actually coming from between the block and the manifold where the reed valves are. It also seems to be coming out under pressure which doesn't make a lot of sense to me unless it is blowing out past the reed valve and/or gasket as the piston comes up. If I understand 2 stroke function, which is questionable, as the piston goes down it is drawing in fuel and creating suction. In that movement I would think it would be sucking air and creating a lean condition if anything, not spraying fuel. Then on the compression stroke the reed should close, so the fuel beyond the reed should never be pressurized, right?
        DSiekman
        2000 Cobalt 293 Twin Volvo 5.0 Gi DP - Sold
        1978 (or 79?) Hydra-Sports 21' CC with 200 Black Max
        2001 F250 7.3 Powerstroke (With a few goodies)

        Comment


        • #5
          Link to video:

          https://youtu.be/5YQD8myKjhQ
          Last edited by dsiekman; September 28th, 2017, 08:40 AM.
          DSiekman
          2000 Cobalt 293 Twin Volvo 5.0 Gi DP - Sold
          1978 (or 79?) Hydra-Sports 21' CC with 200 Black Max
          2001 F250 7.3 Powerstroke (With a few goodies)

          Comment


          • #6
            Wow, that is a lot of fuel. I presume it is not water?

            The only way to get that much liquid fuel in that ares is with a bad fuel pump diagram, I would think. If that is not the issue, and the crankcase cover bolts are tight, you need to look for a crack in the block, likely near or on the crankcase cover.

            Comment


            • #7
              On the other hand, check the enrichener solenoid and hoses for a leak as well. I think it is likely on that side, whereas the fuel pump is on the other side.

              Comment


              • #8
                Originally posted by Chris1956 View Post
                Wow, that is a lot of fuel. I presume it is not water?

                The only way to get that much liquid fuel in that ares is with a bad fuel pump diagram, I would think. If that is not the issue, and the crankcase cover bolts are tight, you need to look for a crack in the block, likely near or on the crankcase cover.
                Yes it is a lot! I already had some fuel on my hands so I didn't smell it but it felt very slippery.

                It is hard to make out in the video, but it appeared to me to be coming from the joint between the block and what I would call the intake manifold. Like I said, I shut it down pretty quickly and I'm a little hesitant to start it up again. I will definitely have my extinguisher handy.
                DSiekman
                2000 Cobalt 293 Twin Volvo 5.0 Gi DP - Sold
                1978 (or 79?) Hydra-Sports 21' CC with 200 Black Max
                2001 F250 7.3 Powerstroke (With a few goodies)

                Comment


                • #9
                  Look like reed bolt screw has a problem
                  When in doubt,Trim it out!!!
                  Business Owner & Certifed Technician
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                  • #10
                    Originally posted by Chris1956 View Post
                    On the other hand, check the enrichener solenoid and hoses for a leak as well. I think it is likely on that side, whereas the fuel pump is on the other side.
                    Top, bottom, and the other side were completely clean, so whatever it is is coming from just the one location. Is the enrichener solenoid the piece that looks like a very small fuel bowl?
                    DSiekman
                    2000 Cobalt 293 Twin Volvo 5.0 Gi DP - Sold
                    1978 (or 79?) Hydra-Sports 21' CC with 200 Black Max
                    2001 F250 7.3 Powerstroke (With a few goodies)

                    Comment


                    • #11
                      Originally posted by Faztbullet View Post
                      Look like reed bolt screw has a problem
                      Is that a common problem? Other than being loose what else could the issue be?
                      DSiekman
                      2000 Cobalt 293 Twin Volvo 5.0 Gi DP - Sold
                      1978 (or 79?) Hydra-Sports 21' CC with 200 Black Max
                      2001 F250 7.3 Powerstroke (With a few goodies)

                      Comment


                      • #12
                        And the saga continues. Cut a hole in the cowl for the exhaust bypass. Engine is MUCH happier.

                        Found one loose bolt and one sheared off bolt. No more fuel leak. I also realized I have to push the throttle really far forward to get an increase in rpm. Iím starting to wonder it the cable is not adjusted right.
                        DSiekman
                        2000 Cobalt 293 Twin Volvo 5.0 Gi DP - Sold
                        1978 (or 79?) Hydra-Sports 21' CC with 200 Black Max
                        2001 F250 7.3 Powerstroke (With a few goodies)

                        Comment


                        • #13
                          New plugs. Now Iím at 5000 rpm
                          DSiekman
                          2000 Cobalt 293 Twin Volvo 5.0 Gi DP - Sold
                          1978 (or 79?) Hydra-Sports 21' CC with 200 Black Max
                          2001 F250 7.3 Powerstroke (With a few goodies)

                          Comment


                          • #14
                            Curring a hole in the cowling is not standard. You might look for an exhaust leak at the base of the powerhead, or an exhaust bypass hose, if you have one. My '93 Merc V6 has such a bypass hose. They can leak.

                            The sheared boat and loose bolt were on the crancase cover? Did you replace the sheared one?

                            What shape were the spark plugs? Was one worn or fouled?

                            Comment


                            • #15
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                              Originally posted by Chris1956 View Post
                              Curring a hole in the cowling is not standard. You might look for an exhaust leak at the base of the powerhead, or an exhaust bypass hose, if you have one. My '93 Merc V6 has such a bypass hose. They can leak.

                              The sheared boat and loose bolt were on the crancase cover? Did you replace the sheared one?

                              What shape were the spark plugs? Was one worn or fouled?
                              No, certainly not standard. My understanding is that the upper cowling is a slightly different vintage than the leg. There was no opening for the bypass hose so it was just pressing against the inside of the cowling and then filling the cowling with exhaust. At idle when not moving it would choke itself out. I used a small hole saw to drill a roughly 1" hole for the bypass hose. With no load it wants to idle near 1200 rpms. In gear in the water it is about 750 rpms.

                              That would be my assumption. The lower half of the bolt is still lodged in place. I lost the head and maybe top 1/4". To replace it will likely mean pulling the carbs. I am going to assume it has been that way for some time, so I will deal with it this winter when I pull the boat.

                              The plugs did not look bad to me. No obvious evidence of fouling that I saw. Insulators were brown, all were a little wet after running, but no other signs.
                              DSiekman
                              2000 Cobalt 293 Twin Volvo 5.0 Gi DP - Sold
                              1978 (or 79?) Hydra-Sports 21' CC with 200 Black Max
                              2001 F250 7.3 Powerstroke (With a few goodies)

                              Comment

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