90hp 2 stroke piston ?

hello all,

i have recently bought a used power head to replace an unserviceable 90etlh. i have no model number for the engine it came from and am having trouble ordering a piston. pistons one and three are in great shape and the block is perfect, so i don't want to mess around with boring it out. i was told the engine overheated and instead of letting it cool after the auto shutoff, the genius just pulled the temp sensor. as a result, piston two melted a little and needs replaced. unfortunately none of the pistons match the specs in my FSM . the two good pistons measure 3.2403" (~82.3 mm) @ 0.39" above skirt bottom, and are marked 6H103. what replacement piston should i buy?

thanks
Jason

[boats.net]

Std bore is 82.00-82.02 mm, may have already been bored to 25mm oversize which would be stamped on top of piston.

ok. i just cleaned of the top of the piston and it indicates 0.50. now i'm really confused. what piston do i have, and what is the replacement part number? how could it be 25mm oversize? that's near an inch.

[boats.net]

Sorry, typo should have been .25mm oversize. Yamaha only has .25 and .50mm oversize pistons.