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Lost speed after change my lower unit

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  • #16
    The numbers don't make a lot of sense. You should be running much more rpm than that with that size prop. The original prop should lower your RPM's even more. I would recommend doing a compression test on the motor, and also making sure that you are getting full throttle on the engine as it sounds like the motor is not making enough power.

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    • #17
      I had already think like you and I did the Compress test. The results: 100 psi in each cylinder. I will check the throttle. I am going to test prop today. Let you know my results.

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      • #18
        Believe it or not with 15 1/4 x 19 I got 5100 rpm 43 mph. I already spoke with the person who sold me the prop. He is change it for a 15 1/4 x 21 to check it out.

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        • #19
          You were totally right. After your observation of something else happening to the eng. I did take it to a Yamaha dealer for check up and they found out the eng was running in 5 cylinders. They rebuild the carbs and now I have the same speed than before. I am getting with a 15x19 prop, (top speed 5400rpm), 49 mph.

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          • #20
            Good, glad to hear your back up and running.

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