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  1. #1

    Default 2003 Yamaha 50hp 4 stroke question about compression

    Hi,

    Thanks ahead of time for any help with this question. I had someone offer me a 2003 Yamaha 50hp 4 stroke today. The price was very good as he needs money. I had him start it in a tank and run it till warm. I then had a friend do a compression test on the 4 cylinders. All plugs were out when the test was done. All cylinders were around 68-70 lbs. I thought outboards were supposed to be around 125 plus, The motor ran great at all speeds and idled perfect. I called a friend who said 4 strokes have lower compression then 2 strokes and if it runs great don't be worried, another friend said i needed to have a leak down test down on a 4 stroke not a compression test. Well I have to decide by tomorrow. Should I be worried about these results regarding the test. I don't want to spend money to end up with a engine with problems. Any advice would be appreciated. I called a few dealers they were not much help.

  2. #2

    Default Re: 2003 Yamaha 50hp 4 stroke question about compression

    "I called a friend who said 4 strokes have lower compression then 2 strokes and if it runs great don't be worried, another friend said i needed to have a leak down test down on a 4 stroke not a compression test."

    i believe you will find 4 strokes have higher compression the 2 strokes. A leakdown test is more definitive. 70 psi is very low.

  3. #3
    Join Date
    Jan 2012
    Location
    Giessendam, Zuid-Holland, Netherlands, Netherlands
    Posts
    102

    Default Re: 2003 Yamaha 50hp 4 stroke question about compression

    I just looked into the Yamaha spec's. 122 PSI minimum!

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