What caused this 2.5 to eat 6 piston pins??

[tony1204au]

Have just torn down this 2004 2.5L carb 200, to discover that it's eaten 6 piston pins.
A big end failure on no. 6 was the reason for the tear down, which now I think was caused by the small end problem.
The other 5 crank journals were perfect, none of the bearings were blue, lots of chatter marks on all 6 rods. Correct amount of small end needles in each rod.
No signs of water in the power head either.
Block has now been resleaved, but hoping to know what caused this so it doesn't happen again...
Engine has about 120hours on it, and doesn't look to have been previously apart.
http://i295.photobucket.com/albums/mm122/tony1204au/Mobile%20Uploads/Barca%202013/CD85ED3A-5586-48C8-98C7-48130B17B1F1.jpg

http://i295.photobucket.com/albums/mm122/tony1204au/Mobile%20Uploads/Barca%202013/17872D8B-2CEC-422C-84F6-283D02B41BC3.jpg

[tony1204au]

http://i295.photobucket.com/albums/mm122/tony1204au/Mobile%20Uploads/Barca%202013/8B46639B-93E2-48B8-8AE5-1E551B2028AE.jpg

[rgsauger]

Maybe a bad heat treat batch from the vendor that made them? What oil do you run? Rpm?

[ChrisCarsonMarine]

Overpropped,long term low level detonation would be my guess...or something else causing slight detonation...too much advance,etc,Chris

[powerabout]

Living on a diet of salty air via the intake
Ex water taxi engine by any chance?
Get the history checked via the serial number

[Dave S]

Wow.....Wow.....never seen anything like that. Some motors blew up local.... Cam 2 oil....too thin....

[Tom D.]

Too much oil!!!

[eli]

yikes something is serious wrong with all the hammer marks and pin wear bad parts and or too much timing and no oil