By that date, most big Force engines used a 3.375 diameter bore. In fact, most later Force engines used the 3.375 bore. It is a standard 3164 Wiseco piston. You can also buy cheaper stock pistons from Sierra or your local Mercury dealer or if you don't want to spend the money Find a junk Force engine from which you can salvage a piston and rod. Pistons MAY be available here at the iboats store
I would offer you a used one but it is not allowed to solicit to buy or sell on the forum. Besides, I need all my good pistons.
If you are looking for a good used rod, send me a private message.
