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  1. #1

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    buying 1997 yamaha gp 1200

    I just recently sold my yamaha ls2000 jet boat and am now looking at purchasing an inexpensive ski. I foun a 97 gp 1200 with 150 hours on the ski and 50-60 hours on the sbt rebuild.(agreed price is $1650 not including a trailer) I am running a compression check and putting the ski in the water for a test run where I plan to run it hard and make sure it operates as it should. I did the stage 2 group k cylinder head mod on my old ls2000 which shares an engine to this ski. I was advised against doing this mod on an sbt rebuild because they say there are too many unkowns about piston size etc.. my questions are these and thanks in advance for any help:

    -what should each cylinder compression be? 125?
    - has anyone here ever done a group k stage 2 upgrade on a sbt engine?
    - how fast should I expect this ski to run top end mph stock?
    - anything else I should know about this model?


  2. #2

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    I dont buy anything with a SBT motor. Be sure to check the hull number. You dont want anything under 500. With that many hours on a hull you could find cracks in the stringers under 500.

    GroupK made a sleeper and hammer kit. Guess you can call it stage 1 and stage 2. But I thought both came with 91 octane cut head which would bring the compression to about 145-150 per cyl.

  3. #3

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    Yeah, the only reason I am considering this one with the rebuild is because I was looking for a machine that would do around 60 mph for under $2000 including the trailer. I was only considering doin the head cut alone, with a solas impeller, which is what I did on the boat (same motors) and it was a great improvement. any idea what stock compression should be?

  4. #4
    DAGO RACING CREW
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    The compression should be 120-125 psi on all three cylinders. Make sure the battery is fully charged and the throttle is held wide open while doing the test. Leave the spark plugs in on the cylinders not being tested, and off course remove all the plug caps.

  5. #5

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    Thanks, I will be sure to run the compression check in this way, appreciate the help and will keep you posted to whether I bought it or not over the weekend.. still wondering about that group k head mod on an sbt engine, very tempting but I dont want a blown engine..

  6. #6

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    I ran a compression check on the motor, 122 psi on each cylinder so I was happy with that. it has very small scratches here and there but nothing major. I took the ski out and it ran amazing so I purchased it. a 1997 gp1200 155 hours on hull and 50-60 on an sbt rebuild, got it for $1950 inlcuding an outlaw trailer in great shape. Anything else I should know before I start using this thing every week? thanks-Pete

  7. #7
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    Quote Originally Posted by pete6053 View Post
    I ran a compression check on the motor, 122 psi on each cylinder so I was happy with that. it has very small scratches here and there but nothing major. I took the ski out and it ran amazing so I purchased it. a 1997 gp1200 155 hours on hull and 50-60 on an sbt rebuild, got it for $1950 inlcuding an outlaw trailer in great shape. Anything else I should know before I start using this thing every week? thanks-Pete
    First thing I would mandate is switching to premix 50:1 if your still running oil injection. After that theres a slew of things you can do for handling/performance (trim tabs, flame arrestors, intake, ride plate...).

    Adam

  8. #8
    DAGO RACING CREW
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    If it still has the stock white trim tabs attached to the hull (they break off), I am sure they are sagging in the middle and costing you several mph. You will need to update the trim tabs to aftermarket aluminum trim tabs.

  9. #9

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    I will have it out in the water this weekend to see how fast it goes and have some fun, and Ill probably convert it to premix the week after that, do I just order/ install blockoff plates on the carbs and remove the oil tank and pump?

  10. #10

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    Quote Originally Posted by Adam E. View Post
    First thing I would mandate is switching to premix 50:1 if your still running oil injection.
    Adam


    I wouldnt go any leaner than 40:1.

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