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  1. #1
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    what caused this?

    2.5 175hp efi. very little time on rebuild. no buzzers. what do you think caused this? top of the piston only had minor damage from metal that got on top of it. it didn't look like a normal detonation meltdown piston. it wasn't even stuck in the cylinder.
    these are pro marine bearings and part of the bearing carrier was broken out in 3 of the other good rods. anybody else seen this?
    thanks

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    Last edited by mercrazy; 04-27-2012 at 03:17 PM.

  2. #2
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    Piston stuck, good job on the rod! I have'nt seen one that bad in a long time!

  3. #3
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    I'm not a pro mechanic but have some theories. Rod not torqued properly or too much slop from wear or rod alignment tool not used.

  4. #4
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    Cold seize possibly
    "One of the penalties for refusing to participate in politics is that you end up being governed by your inferiors". Plato .

  5. #5
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    i've never seen a stuck piston break out the wrist pin. i'm not sure i'm a fan of these pistons if that can happen. most of the seizures i've seen just lock down the engine.
    no comments on the web missing out of the bearing carrier?

  6. #6
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    The captain has it figured out. Sorry man it's going to cost a hole bunch. Thanks Martin

  7. #7
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    One of my old motors burn up a piston at 4 grand right after I run it for bout 2 miles at 7 grand. It gave about 1 second worth of warning (loss of power) before it siezed up and slung a rod through the block after it pulled the wristpin out of the piston. So it can happen anytime...just pissed me off that it did all this damage a 4 grand. I went through the carbs and checked the electrics when I put everything on another block and there was no explanation for the failure.

  8. #8
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    Captain got er nailed it stuck maybe lean out from doublefireing switch box you check um how much time on rebuild 10 hours or 10 minutes

  9. #9
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    Quote Originally Posted by mercrazy View Post
    efi.
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    Injector most likely... You know your really cool when your pulling wrist pins out from behind the propeller.

  10. #10
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    Yeah you stuck the landing on that one,also believe your rod bolts were over torqued,what brand of piston was it,and how much time did you have on it,tell us a little more please,I vote cold seize or double firing
    21 SuperBoat VF200 Yamaha SHO
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  11. #11
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    probably 20 hours on rebuild. it was #6. pro marine pistons, bearings, and bolts. injectors were cleaned and flowed. the builder did the 30lbs.+ 90 degree. i warned him. it has a rapair trigger. i still don't understand the multiple carrier failures. thanks for all the replies.

  12. #12
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    What is a double fire and what would cause a piston to stick? What,s a cold seize?
    Last edited by rgsauger; 04-28-2012 at 12:27 AM.

  13. #13
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    Double fire is when the coil fires at its normal time and then fire again after that....as in 2 fires per 1 revolution of the crank....this is the same as advancing the timing way too much which leads to detonation. My 2.5 steel bore tore up at 4 grand after running it about 2 miles at 7 grand when it was stock except the heads and older style electrics with an oring head style block. It gave a 1 second warning with loss of power and it puked. I started it back up and thought is was the gearcase at first cause it wouldn't go into gear. Well it slung a rod though the block right where the cables mount up but it'd still run off 5 but a wee bit rough. I checked the carbs and electrics when I put it back together and couldn't find anything wrong with it....ran great till a few months back when #3cold siezed just a little b/c of washers instead of t-stats. Motor still ran great but figured I'd pull it down to give it the works.....lesson learned- only run t-stats in a steel bore motor...even if it is wore out with plenty of clearance. 6 grand is fine with washers but 7 grand is not.....I learned the hard way with my steel bore.

  14. #14
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    Almost as bad as this on. Definately a stuck piston. Oh and finally found the wrist pin when I removed the lower unit.

    Last edited by HStream1; 04-28-2012 at 07:09 AM.
    Bud Conner "Heathen" "Defending Our Constitution"

    FOR ALL ENGINE APPLICATIONS
    DRY Film Lubricant for Piston Skirts & Cranks + Thermal Barrier Ceramic Coatings for Piston Tops, Combustion Chambers, Valves etc !!



  15. #15
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    Looking at the carnage,it appears that the maincap parted ways with the rod first,as it's fairly unbent. The fact that you have bearing cage issues in the other 3 rods says you had clearance issues during the rebuild.

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