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  1. #1
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    Need Top Pin Piston Explained

    Been searching through google and found a few threads. Some of it requires digging or I'm not working it right. I am looking for the advantage of the top pin pistons. Also an explanation of what it does would be great as well. Sorry if it's a stupid question, and if there is a good thread on this please point me too it. Thanks
    Respect no wake zones!!! Evinrude guys need a place to race too.

  2. #2
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    The pin that holds the rings can sometimes come loose especially when run lean so instead the pin is removed and instead installed from the top of the piston.


    18 ft Speedcraft - Offshore

    Bottle Fed Merc tuber 2.4

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  4. #3
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    18 ft Speedcraft - Offshore

    Bottle Fed Merc tuber 2.4

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  6. #4
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    If you was gonna be runnin Miles and miles at 8k rpm and cutting it close on jetting or fuel mixture (efi) it is a good safety precaution but not necessary (unless racing) , like David said , unless run lean or get very hot ,u wont have any issues with side pins. Also top pin makes the ring gaps line up , which is ok for that set up. Some say leak down #s mite b higher on top pin cause ring gaps. This is just from reading. I've never had a set top pinned,

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  8. #5
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    But which is better, top or side pinned, I can't wait to read the answers
    97 xb2002 15" 300x w 1.62 sporty
    ( Haulin Bass) (108 mph so far
    (Rip. Whiteally02) -dad
    They call it the American dream, to bad you have to be asleep to believe it. - George Carlin

  9. #6
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    From the studying I have done top pin is needed for higher rpm applications like racing. But if not done correctly it can lead to piston failure and more harm than good. Just what I have read.
    Respect no wake zones!!! Evinrude guys need a place to race too.

  10. #7
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    Quote Originally Posted by Will hedrick View Post
    But which is better, top or side pinned, I can't wait to read the answers
    If you are certain that the pin on the side-pinned piston will not come out and create damage, there is no point in top-pinning.

    Top-pinning is like insurance. The need for that insurance depends on the type of piston and application.

    I had a pin come out once from a brand new piston and crack a sleeve after only a few hours of running time.

    So I decided to have top-pinned pistons in future engines.__PRESENT
    Markus' Performance Boating Links:
    www.toastedmarshmallow.com/performance

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  12. #8
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    Nicely stated
    97 xb2002 15" 300x w 1.62 sporty
    ( Haulin Bass) (108 mph so far
    (Rip. Whiteally02) -dad
    They call it the American dream, to bad you have to be asleep to believe it. - George Carlin

  13. #9
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    And if the pin is not welded and you can see it i have had pieces of pin break off and ruin a piston,head and bore ,i guess i dont understand this whole thing between boat motors & snowmobile engines are all cast pistons side pin and for the next 5000 miles or so are run at 7000 rpm or more hold up just fine i know many blow up because of fuel issues or heat ,i have run all top pin in my outboards and have had failures from top pins not the welded ones so now im running vertex side pin in ff blocks so we will see down the road how all goes if these blow then its flower pots

  14. #10
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    Quote Originally Posted by Markus View Post
    I had a pin come out once from a brand new piston and crack a sleeve after only a few hours of running time.
    What decade did that happen in ... ???

    No need in throwing the piston mfg. under the bus .. just what year ( approx. ) time frame ...

  15. #11
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    To the OP, I wouldn't worry about top pinning pistons at this point. If you end up needing it done you will learn about it at that time (and the reasons you need it will be self evident). If you are going down the rabbit hole of building and modifying outboards for high performance use you will probably scatter a few powerheads before you need top pins...

  16. #12
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    Good info guys. I dont see me needing top pins as I dont need another racing hobby lol. Was just curious as I have heard both sides in some posts but never any specifics. Always just "this is better" or " have to do this" lol, never followed by any science.
    Respect no wake zones!!! Evinrude guys need a place to race too.

  17. #13
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    There's plenty of good reading about top pins and really anything else regarding the V6 merc outboards on here, search is your friend. Literally MONTHS of good reading...

  18. #14
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    Quote Originally Posted by Chaz View Post
    What decade did that happen in ... ???

    No need in throwing the piston mfg. under the bus .. just what year ( approx. ) time frame ...

    The 1990's early 2000's was a tough time to be a locating pin.

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  20. #15
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    Quote Originally Posted by Capt.Insane-o View Post
    The 1990's early 2000's was a tough time to be a locating pin.
    Two decades have gone by since the fix ... and the horror stories still run rampant.

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