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8hp dying on acceleration

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  • 8hp dying on acceleration

    2005 8hp 2 stroke 8MSH. Did my annual decarb where I sea foam the motor. Changed fuel strainer, plugs. Ran fine for about a week then randomly started smoking a lot and rough. Kept getting worse and worse. I pulled the carb and completely cleaned it in carb dip. Jets, pilot, etc. Put back together.

    Engine primes fine. In fact primer bulb stays hard all the time. Will start easily with choke on but as soon as the choke comes off it tries to slowly die. When you rev it up it will rev but if you hold it at higher rpm it dies. And it smokes something fierce. Very light blue white smoke. The plugs are white and wet with absolutely no carbon even after about an hour of total run time.

    So I have a new fuel pump and fuel strainer on the way. Any other thoughts what might be going on? Maybe ignition?

    Thanks

  • #2
    Oh and I check compression... it builds to 160 psi over 5 to 6 pulls. Also ran the motor on an auxiliary tank and it acted the same.

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    • #3
      Is it pre-mix or have oil injection?

      Maybe post a pic of the spark plugs plz?
      Scott
      1997 Angler 204, Center Console powered by a 2006 Yamaha F150TXR

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      • #4
        Have a look down the spark plug holes and see if the tops of the pistons are shiny clean, if so, you are probably getting water in the cylinders...steam cleaning them and the plugs.
        Post a few pictures,as already stated.

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        • #5
          Dang... spark plugs are clean except the ground strap is black. Piston tops have almost all the carbon removed. Last time I checked I had normal piston wash.

          I'll try to post pics but I live in the sticks

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          • #6
            Have to post the pics tomorrow when I get out of the jungle.

            So if it is water.. is that just a head gasket? Piston Walls dont look great but compression is 160 each hole after 5 to 6 cranks.

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            • #7
              Originally posted by mitch184 View Post
              Have to post the pics tomorrow when I get out of the jungle.

              So if it is water.. is that just a head gasket? Piston Walls dont look great but compression is 160 each hole after 5 to 6 cranks.

              ^^^, Probably... You'll still get good compression as the failure (hole in gasket) is likely very small sucking in water..

              A leak down test, pistons at TDC, will probably show leakage once pressurized.

              Scott
              1997 Angler 204, Center Console powered by a 2006 Yamaha F150TXR

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              • #8
                I was thinking 160 PSI is high for a 2 stroke,
                do all those small motors have higher compression?

                what all ways are there for water to get into the combustion chamber?
                water in fuel might get thru the carb, but not likely if motor runs well.

                head gasket, hole in head or block maybe.

                could it get in from a exhaust cooler plate hole?

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                • #9

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                  • #10
                    160 did seen real high for a little 8hp. Especially with 35 degrees of timing.... but the service manual states compression pressure at 153 psi with a comp ratio of 7. So I guess that's normal.

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                    • #11
                      Yep, that plug is way too clean...
                      Scott
                      1997 Angler 204, Center Console powered by a 2006 Yamaha F150TXR

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                      • #12
                        So am I looking for the "power head gasket kit" or is it just the "gasket, head cover 1"?

                        I believe i just need the kit but I cant seem to find what all the kit entails.

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                        • #13
                          buy what you need to do the job.
                          some times the kits are higher and include stuff you do not need, some times they are cheaper and do not include everything needed

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                          • #14
                            So I'm having trouble finding the part number or even a schematic that has the actual cylinder head gasket. Exhaust gasket, cover gaskets... but no head gasket. I would think the powerhead gasket kit has it but no one can confirm.

                            Anyone have another source to get the actual head gasket PN?? 2005 8MSH

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                            • #15
                              I am seeing the same as you...no head gasket in the power head repair kit. Or a parts break down showing it on this site anyway.

                              Hopefully Mr Boscoe will chime in here and dig it up for you....he is very good at that!!

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