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  1. #1
    dcuhpw's Avatar
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    Crankshaft play spec

    Checking for crankshaft play is an important thing to do in a used ski since jet pump failures have been known to happen (especially on older ultra 250x/260x and even 15f). However, it should be noted that every engine I have ever checked always has some play especially if the oil has been drained and then engine has been sitting for a while. I donít see a factory spec for crankshaft play (fore and aft) but was wondering if anyone had this spec. There has to be a tiny bit of play to allow for oil to penetrate the area and leave a film. My current engine has zero metal shavings in the oil and turns over great (waiting for head machining to complete). It has .003 of play with all oil drained and the engine sitting cold. Measurement was taken with my dial indicator. What is the service limit for this spec so we can reference what is within spec? Car/truck engines Iíve built in the past all have a spec normally between .002-.006 and a well worn engine may have up to .010. If anyone has a spec that would be greatly appreciated!

  2. #2
    Look in the manual I believe there is a spec for clearance on the thrust bearings when assembling the engine. I suppose you could interpret that as end play once fully assembled.

  3. #3
    dcuhpw's Avatar
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    Quote Originally Posted by mwhc View Post
    Look in the manual I believe there is a spec for clearance on the thrust bearings when assembling the engine. I suppose you could interpret that as end play once fully assembled.
    Don’t see any spec listed (can’t find it at least). Looked up specs on racing engines and they are normally between .004-.008.

  4. #4
    Could have been rod side clearance let me look when I get home

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    dcuhpw's Avatar
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    Quote Originally Posted by mwhc View Post
    Could have been rod side clearance let me look when I get home
    Just found it. Its referenced as crankshaft side play. Spec is between .002-.0094 with service limit at .017. That's a really big range! Suffice it to say, my .0035-.004 is well withing factory spec. For future reference, if you are able to move your crankshaft in and out a tiny bit and even hear a light taping sound from the crank when you do that, it's perfectly normal. Don't assume you have a a trashed thrust bearing. Get a set of dial indicators in .001 increments and measure it. A decent set of dial indicators will set you back $50 or so and you could easily do this test while the engine is in the hull.


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