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  1. #1
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    Help with disabling oil injection and cylinder bore. (Mercury 2.5L)

    Hey guys! long time reader, first time poster!

    Engine:
    1997 Mercury Sport Jet 175HP XR2
    Starting serial numbers: OE272

    I have 3 pistons with stuck rings... So while taking the engine apart, i made it to the crank case and found my oil injection system to be trashed.. the plastic gear is stripped and the oil pump bearing is seized.. So I want to know what is the best way to disable the system but retain the overheat alarm?

    Second,

    When I took readings of my cylinder bores, my lowest value for one cylinder is 3.479" (4 reading per cylinder, 2 top and 2 at bottom at 90*) but my shop manual says the standard bore when new would of been 3.501.. My cylinders got smaller?? i have a bore gauge with the 3.4" adaptor and the .1" spacer.. for a total of 3.5" measured with a caliper. then my gauge would read, in this case for example, 21. So that is 3.5" - 0.021" for 3.479".. What am I doing wrong? :/ My plan is to hone the cylinders and install new rings... but i want to make sure I'm still within specifications.

    Thank you!

  2. #2
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    Bump!

  3. #3
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    ok... I'm an idiot.. I was not using the bore gauge properly... I zeroed the gauge on a caliper to 3.501. Now my worst cylinder reads 3.5 on the gauge... So by my calculations, that would mean the cylinder is 3.501 + 0.035 for 3.531".. yikes! that's bad right?? Will boring the cylinder to 0.030 over be sufficient?

    Thank you!

  4. #4
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    Welcome to the site. I am not sure you are measuring correctly. If you bore guage reads 3.5 why are you adding .035? I use my bore guage zeroed in the cylinder then measure guage with a micrometer. If you bore is truly 3.531 and would clean up at that measurment, you would be OK with .030 pistons but if it is measuring 3.531 before honing I doubt you will end up in spec. According to above post you are really at 3.536 and not 3.531. 3.501+.035=3.536 which means you will need to bore to .044 and buy new pistons.
    As far as oil injection goes just remove pump and gear and install propper block of kit (avialable from Merc or Pro Marine) and remove module. Good luck.

    Rock
    Team Junk

    No sparkling wiggles in here, only dump truck grinches.

    "Screamin Heathen"

  5. #5
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    Set a micrometer to your Bore size. Zero your bore gauge to the micrometer. Now send the bore gauge down your cylinder. What is reads is your wear. maybe something like .002 or .004. In your book will be how much is OK.

    Good Luck and Welcome!

  6. #6
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    I set my bore gauge with a caliper (not as accurate I guess.. ) I set it to 3.501" at the zero mark.

    Then put the bore gauge in the cylinder. It read 3.5 counter clockwise.

    I have attached a picture of my bore gauge dial.

    Am I correct in my understanding the 3.5 on the gauge is 0.035"? making my bore size 3.536?

    I seem to be doubting myself on everything now. :/

    Click image for larger version. 

Name:	bore gauge.jpg 
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  7. #7
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    On your dial indicator each individual mark on that face represents .0005". When you zero your bore gauge you zero it at 3.5000" and then run the bore gauge down the bore in several locations. If the needle travels 20 marks on the dial indicator you are at 3.51". If it travels 35 marks you are at 3.5175" etc..
    Last edited by wired247; 06-26-2014 at 05:19 PM.

  8. #8
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    Quote Originally Posted by wired247 View Post
    On your dial indicator each individual mark on that face represents .0005". When you zero your bore gauge you zero it at 3.5000" and then run the bore gauge down the bore in several locations. If the needle travels 20 marks on the dial indicator you are at 3.51". If it travels 35 marks you are at 3.5175" etc..
    Excuse my ignorance here. I'm a computer Engineer and that probably makes me extra stupid... :/ I thought the 0.005" meant its accuracy and the 0-.25" meant its range?

    When I zeroed the gauge at 3.501, anything smaller than 3.501 would register clockwise (subtract the value to the 3.501") and anything larger (like my worn cylinder) would register counter clockwise (add the value to the 3.501").

    I thought every large tick was 0.01" and every half tick is 0.005". so 3.5 ticks is 0.035" ?


    Don't get me wrong, if what you are saying about my gauge is true, that is great news for me!

  9. #9
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    Dont feel bad. I'm a Mechanical Engineer and I cant figure out how to log onto my desktop at work sometimes. The graduations are .0005" . A half sweep of the gauge is .025". Overall gauge travel is .25" but thats after many full dial sweeps.
    Last edited by wired247; 06-26-2014 at 06:52 PM.

  10. #10
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    Wow! this might be good news! so with 3.5 ticks I add .0035 to my 3.501 initial reading? So my blown cylinder is really at 3.5045? Meaning it is probably hoanable?

  11. #11
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    bump!

    This measurement can cost or save me $600+ in piston.

  12. #12
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    Make sure you measure your pistons too. A cylinder can be in spec but the piston can be callapsed at the skirts. You will end up with way too much clearence.

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