Need Oversize Piston for M2 240 EFI

[yama0918]

I bought a 2001 Challenger with the Mercury M2 240 EFI. The engine was bad when I bought it and cylinder #3 is bad.

I removed the piston and the cylinder wall does not appear to be too bad. You can see the marks on the wall but can barely feel anything with your fingernail. You can feel the ridges with the tip of your finger. The manual states that the finish hone should measure 3.501 in (88.93 mm). My cylinders measure as follows.

Starboard Cylinders
Cylinder #1 measures 3.497 in or 88.84 mm
Cylinder #3 measures 3.502 in or 88.94 mm
Cylinder #5 measures 3.498 in or 88.85 mm

The manual shows there is an .015 in (.381mm) oversize piston so the finish hone should be 3.516 in (89.31 mm).

Can someone tell me where I can find an oversize piston? I would prefer .030 just in case I need to bore out larger. Also, any ideas what may have caused this in the first place. I would hate to fix it without finding the cause.

 

[koby6587]

tri state marine go on eBay and type in 240 efi power head and go to the guy that has a rebuild kit for 880 and call him I bought a.20 oversized piston for my challenger a few weeks ago he has all different sizes for oversized, make sure if you order piston rings for the original size pistons to make sure they are 1.5 mm they sent me 2mm which would not fit in the stock ring grooves the new aftermarket WSM Pistons use the 2mm just double check