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  1. #1

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    how to check if a motor can run or is good - 4stroke

    I want to buy a "running" 4 tek motor for my blown up ski. I found a working motor that is outside of a hull. On a bench what can you do to see if the motor works?
    how can you compression test it?
    how can you turn it over to see if it is free and able to turn

    Scope the cylinders? How can you look at pistons or crank? Pull the head?
    can you stick a battery to the starter and see if it turns over?
    Any ideas?


  2. #2
    Sanfish's Avatar
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    Quote Originally Posted by taillight View Post
    can you stick a battery to the starter and see if it turns over?
    Any ideas?
    Yes, just use jumper cables making sure the ground has a good connection. You could get fancy and run a high amp marine on/off type switch box. I wouldn't buy a "running" motor unless I can at least run a compression test. Cycle the motor without spark plugs first to make sure no fluid is in there (owner could add a little oil in chamber to fool a psi test).

    If price is low enough, pulling the head and oil filter inspection can show a good amount of information.

  3. #3
    Guidoo's Avatar
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    I'd at least check the compression and oil pressure. Or if you have access to a leakdown tester.

  4. #4

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    how do you check compression. the motor is sitting on a table. hook up a battery to the starter? will it not shake and slide off the table? Im new to 4 strokes

  5. #5
    Guidoo's Avatar
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    Sure it will move somewhat. It won't flop around like a fish on the shore. I watched a buddy fire up a 440 Chrysler while sitting on his garage floor. If you do try cranking it,be sure it has oil in it and sitting upright as mounted in the hull. You don't want to crank it without oil getting to the rotating assembly.

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