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  1. #1

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    98 seadoo xp compression

    so i have a 98 seadoo xp, i have only had it about a month now and it runs perfectly! never had reason to suspect anything was wrong with the engine. well, i was in harbor freight the other day and bought a compression tester just for kicks. well to my horror i found i only have 90psi in each cylinder! weird because it runs amazing! no bogs, all the power is there, runs fine even after its warm. i cant explain it, do you think i bought a lemon for a compression tester? and is a top end rebuild a DIY job for someone with mediocre mechanical ability? and before i get spammed, yes i did in fact hold the throttle open while testing the compression. Also, would it hurt to put a few more hours before a rebuild? i dont ride hard and generally just cruise but could running it with low compression really hurt it too bad?


  2. #2
    SURFnTURF's Avatar
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    If it is 90 it is too low,but I would check it with a known working gauge at the very least. Is the tester the screw in type or just the hold over the hole type ?
    What is the max rpms it achieves because they will be low if it is 90.Usually a good engine will run 6850 stock.

  3. #3

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    you are right about the RPMS, i run right at 6000-6500 in water and 7k out. i only run about 45 mph top speed on glass with trim all the way up. your probably right, can i get away with just rings or will i need to bore and upsize the piston?

  4. #4
    SURFnTURF's Avatar
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    You are missing out on a lot of torque and top end speed . You need to pull the head of first and inspect the bores, usually if both bores are 90 means its done a lot of hours and is tired and will need a new top end. Why dont you have ago yourself and pull it down when the engines out and learn how the engine works .When you do this you appreciate the importance of good maintenance and try to reduce water intrusion as this is a problem on 98xpl.
    Guys here will talk you through it as there is great info here.Pictures can help you as well.

    And you can download a manual,this is invaluable for a novice.
    Here http://seadoomanuals.net/manuals/199...hop-manual.php

  5. #5
    I have one of those HFT gauges and it reads about 40 PSI LOW. Also, the XP has quite a bit of extra rotational mass (midshaft) and the condition of your battery/starter has a direct effect on compression readings. If your gauge is as bad as mine, you're right at stock 130psi.

  6. #6
    rhyne717xp's Avatar
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    The Harbor fr8 compression gauge I have works gr8. I read 170 psi each hole with 1.35 squish. Mine has been consistent for years.

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