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  1. #1

    need gpr help please

    2001 gpr 80ish hours on it...pump seal kit new wear ring last year..clear.is great...no cavitation.... d plate free flow exhaust.steeped sponsons..and all last year....68 plus on gps and few times low on gas got 69 ...gpr was a top end monster for not gettin into motor....slug out gate,,,,,but i knew that with 14 20 set back......and on gauges,,,,showed over 7k rpms,,,,it was perfect.....late last year.....started slowin up....to the point wouldnt even go 50 mph......figured it out.....losing one cylinder.....compression.....number 1...118 psi......number2 120psi,,,,,number 3 85 psi......there was my problem.....took it to local mechanic in ocean city md....i wont say his name......i asked for whole rebuild....got back 2 month ago.....ran finr for my girl to drive it while i was on my other ski....she had no complaints.....well this where it gets interesting....i drove it while my boat was down....took a trip without my gps...with some fiends....rode fine...but to me seemed slow...plained ok...turned great...no cavitaition....but had no gps......rode it for second time today with gps and fastest i could get was 62.....wtf......where did my mph go....so after checking everything....it all seemed right.....then after all my problem solving deduction......i was at 6900 rpms....so why the loss in almost 300 rpms....i figured motor dosent have enough ass to mafe the 14 20 setback work like before.....checked everything again.....trotle cable to impeller...everthing ok....even checked gas and fuel filter.....nothing......its always the last place you look...checked compression.....on 3 different gauges.....100 across the board....all even but 100psi....wtf......isnt a new motor at least 120 psi......and would that 300 rpm loss equals 5plus mph.....and any sudgestions considering i have only 8 hours on new motorwhat would you do.....im asking.....because.....i paid alot of money....and it slower......it was a proven mph boat...


  2. #2
    Did they put in a SBT motor?

  3. #3
    No....rebuilt. ...why do ask....but would the 300 rpm loss make me lose 5 plus mph.?

  4. #4

    Join Date
    Jun 2015
    Location
    Kingfisher, OK
    Posts
    89
    Was a proper break in performed to seat the new rings?

  5. #5
    100 psi is low.
    If everything else is correct ie jetting pump hull prop.... Then the issue is the motor. Be 100% you did the test correctly. Add a tablespoon of oil the bore and retest. If the numbers come up its usually rings. What do the plugs look like?

    Are the jugs sleeved? If so how did you winterize the ski? Rings stick to cast iron if not properly winterized.

  6. +1 by:


  7. #6
    Plugs look fantastic...and yes break in was right.....the evidence I have.....100....on all three....so whatever it is is happening on all 3 cylinders I'm taking a guess and I bet you that the gasket for the heads is too thick and that's why the compression is low also I bet you if you looked at the squish its not a lot so I think its too big of a head gasket but my question still remains would the 3 hundred rpm loss be enough to reduce 6 7 or 8 mile an hour loss on the top side I'm thinking in my because the motor just doesn't have enough ass to make the 1420 work like it did before but I don't have any experience in this can anybody chime in on this

  8. #7

    Join Date
    Jun 2015
    Location
    Kingfisher, OK
    Posts
    89
    Drop a table spoon of oil in the spark plug hole and test it. If I comes up its your rings, if it doesn't change it could be head gasket maybe. Lower compression will limit your power to turn the prop. You had 120 psi before to turn the 1420 and now you have 100psi and can't turn it.

  9. #8
    you just confermed what i was thinking.....i talked mech.....he said he will use diff,head gasket...and squish test.....and will bring back to 130.......cant wait.......70 plus.....here i come....lol\

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