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2000 Tohatsu 50 problem

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  • 2000 Tohatsu 50 problem

    My neighbor's Tohatsu 50 is not running right so he asked me to help him out.

    The issues are this motor idles rough, dies at idle at times and surges intermittently at cruise.

    He ran it thru some sand/mud 2 years ago and overheated the engine. He had diagnosed by a local mechanic and he found low compression on the #2 cylinder and water on all plugs. He installed a new head and gasket and cleaned the exhaust plates and installed a new exhaust cover gasket. The motor ran well at first but the performance has been getting worse over time.

    The first thing I did was pull the plugs and I have never seen plugs in this condition. They are a brown/tan almost rusty color and really look like they have been sitting in water. The middle cylinder was the worst of the three.

    We put in new plugs and ran the boat at speed for around 20 minutes and the afterwards the new plugs looked nearly as bad as the old. Could the head gasket be leaking allowing water into the cylinders? Compression is 120 on the top and bottom cylinders and 115 on the middle. Any insight would be appreciated.

  • #2
    Re: 2000 Tohatsu 50 problem

    Possible. Pull the head and do an inspection checking for carcks in the block and warpage of the cylinder head.
    Elvin
    My answers are like Zen...It may not be the answer you want, but it is generally the answer you need.

    The 3 Rules:

    1) Look in your service manual first...Then ask me if it is correct.
    2) Understand that your desire to repair your engine does not mean that you have the ability to do so.
    3) If you are confused, take your engine into a dealer..Then let them be confused...At least, in theory, they sent someone to outboard 101.

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    • #3
      Re: 2000 Tohatsu 50 problem

      Originally posted by TOHATSU GURU View Post
      Possible. Pull the head and do an inspection checking for carcks in the block and warpage of the cylinder head.
      Just so I'm on the same page, does the condition of the plugs as I described sound like water is getting into the cylinders?

      Also, does the way it's running sound like water intrusion as well? I am only asking because I have repaired many issues with ob's but have never encountered this specific problem. Thanks!

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      • #4
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        Re: 2000 Tohatsu 50 problem

        If engine experimented a severe overheat condition, as stated by TG, probably head is warped, gasket is not sealing properly against crank case letting small quantities of water being combusted with fuel. Definitely plugs will look rusty.

        Happy Boating


        Sea Rider 320, 380 Sibs, 450 Rib, 2 Strokes Tohatsu 5,18 & 30 HP Proud Smokers

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