Rebuilding 200HP HPDI

[rbablitz]

I'm in the process of rebuilding a 2001 200HP HPDI.
The Yamaha service manuel states that cylinder #1 piston has a different dimention from the others. It also states the cylinder bore dimentions are the same for all the cylinders (including #1) as well as the piston rings. The parts manuel states all pistons/rings are the same part number (with the exception of their respective sides).
Does anyone know why Cylinder #1 is different or why? And why the parts book says they are all the same? Lost on this one.

[boats.net]

All the cylinder bore are the same. The parts book list port and starboard pistons, cyl. 1, 3, and 5 use the same piston.

[rbablitz]

Thanks for the reply. Had a feeling all pistons should mic out the same. I'm going to go ahead and install the pistons. Any idea why the manuel says #1 is different? Yamaha states #1 should be 3.5372-3.5381 and #2-#6 should be 3.5392 - 3.5400. Just curious.