9.5 OMC leaking exhaust question

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  • April 27, 2015 at 6:23 pm #1342
    johnyrude200
    Participant

      I have been lucky and haven’t run into one of these yet (it will happen eventually). I was wondering, if one of these leaks are present, when you remove the cowling would you see exhaust billow out. Does it present as the motor dieing out at the low end, and is a simple test to run it with the cowel off and with it on to see if there is a difference.

      I have a 9.5 that seems to be blubbering big time independent of if the cover is on or off (so I don’t suspect exhaust leakage as the culprit). Adjustments to the carb are helping it, but it is a situation where if I lean it out at the top end to get it to run a bit smoother (still bubbering at the top end), it stalls at the low end. I am thinking the high-speed orifice might be toast on this carb, because I cleaned the carb and it looks pretty good, and the ignition system is very strong. Compression is acceptable (idles down fairly low, between 65-75PSI cold).

      With the pickup, I tried setting it to pickup later and that didn’t improve the situation, only made it fuel starved at the top end. Setting the pickup earlier just made it blubber out and die with anything above idle.

      My next step was going to be to swap out the lower carb half (where the high speed orifice is) with a NOS carb, see if that improves things. If not, I guess I could pull the manifold to take a look at the leaf valves but I don’t think that is the issue, unless they are somewhat stuck shut.

      April 27, 2015 at 6:52 pm #14870
      johnyrude200
      Participant

        UPDATE. In my search to determine what was going on, I found water in the cylinders. As FrankR has been so kind enough to point out, that water can come in through a leaky exhaust baffle. I have already pulled the cylinder head and turned the flywheel over a few times, and I will say there was a HUGE gush of water that came in through the exhaust ports into both cylinders, with the white froth. It was at least 12 ounces of water.

        I will replace the head gasket (although it looks completely fine) to see if this improves things. If not, looks like I’ll be into a full teardown on this baby to investigate further.

        April 27, 2015 at 7:54 pm #14875
        frankr
        Participant

          US Member

          Obviously, if it is coming in through the ports, the head gasket has nothing to do with it. May as well save the gasket for reassembly after you do the powerhead repair.

          It’s interesting that it was a HUGE gush of water. Must be quite a leak.

          April 27, 2015 at 8:13 pm #14877
          johnyrude200
          Participant

            It ended up being the inner exhaust gasket. There is a spot where the water circulates to keep the port side (exhaust side) cylinders cool, right where the exhaust is at it’s last point before going into the lower housing. There was a 2" gap in the gasket, allowing water to gush in. I think why there was so much water when I turned the flywheel over (with cylinder head removed), is once the motor was shut off, of course, any water at a ‘high point’ above this leak just started backing it’s way down.

            I could hear gurgling going on once I shut off the motor too from that area.

            Fortunately the lessons I learned back in January during the last batch of these I was working on taught me a great deal about how to pull them apart completely and where to look.

            Thanks again Frank! School of hard knocks as you say! Recall the advice you gave me about that 18hp motor with the 1" diameter hole in the exhaust baffle. Still have that baffle as a conversation piece for others!

            April 27, 2015 at 9:44 pm #14883
            frankr
            Participant

              US Member

              Boy, you got that torn down pretty quickly. I’m giving you a "A+" on that.

              April 27, 2015 at 11:25 pm #14890
              johnyrude200
              Participant

                Well, this one was a miraculous unit…all the screws came loose just under muscle strength. Tends to make things go a lot quicker. Plus getting some guidance from generous folks like yourself and the other regulars helps noobs like me gain some street smarts.

                I’d say it took about 2 hours teardown to rebuild. 3rd pull, fired up, and she runs totally normal now.

                April 28, 2015 at 12:09 am #14893
                frankr
                Participant

                  US Member

                  And you got it put back together and running already!!! You get another "A+"+++

                  April 28, 2015 at 12:15 am #14895
                  johnyrude200
                  Participant

                    Frank, you guys are keeping the motors alive by passing on your experience and knowledge. The books just don’t have the answers….!

                    April 28, 2015 at 12:49 pm #14922
                    johnyrude200
                    Participant

                      my original question though – if there is a leaking exhaust, does it choke out the motor, and if you remove the cowling is it fairly obvious there is exhaust visibly and smell-wise?

                      April 28, 2015 at 1:02 pm #14923
                      cajuncook1
                      Participant


                        The 9.5hp Evinrude/Johnson motors were known to have exhaust leak issues that would make a motor run poorly. Also, vibration dampeners were not added to the motor until late 1966 and definitely in 1967. So, the 1964 to 1966 motors idled a bit rough due to the excessive vibration, so the dampeners and slight carburetor adjustments improved idling from 1967 an on.

                        Suggestions:

                        – If you are running this motor in a barrel, then put a fan next to it so the fan can blow the exhaust gases away from the motor. The 9.5hp motor was built compact and sits low in the barrel, so it has a tendency to inhale its own fumes and idle and run very poorly. (Usually not a issue on the open water and while running and moving along.)

                        – If the fan does not help much, then remove the motor cover. If the performance improves then you have a exhaust leak issue.

                        There are four known areas that can leak exhaust gases inside the motor cover and smother the motor. That is why you have rev up the motor to run rich to stay running.

                        Leak 1 = Is in the first attachment picture and is part # 87 SEAL,Exhaust housing. If torn, cracked, miss shaped over the years or trash collected in between the side and exhaust housing then exhaust gases can accumulate up near the motor.

                        Leak 2 = Is in the first attachment picture and is part # 43 HOSE,Exhaust. If cracked, torn or loosely clamped then exhaust gases can escape and accumulate in the motor cover and smother the motor.

                        Leak 3 = Is in the first attachment picture and is part #78 BOOT,Shift rod. If torn, cracked or missing then exhaust gases can escape and accumulate in the motor cover and smother the motor.

                        Leak 4 = Is in the second attachment picture and is parts #6 SEAL,Impeller housing and part #7 WASHER,Seal. If missing then exhaust gases can escape and accumulate in the motor cover and smother the motor.

                        Image number 1

                        Image number 2

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