Outdrive is mounted 1" off-center?

Well, the title pretty much says it all. As I'm restoring a 1967 24' Piranha, there are all kinds little suprises along the way. I put a new plywood transom in the boat last fall and am now ready to cut out the key hole for a Volvo Penta 270 drive. I thought I would just cut it exactly where it was by using the existing outside glass skin as my pattern; however after going over it a few times it's become apparent that the drive was mounted 1" off-center to the starboard side. Is this done on purpose? Or a simple math mistake?

This boat always had a problem with hard steering starboard. It seemed adjusting the trim fin on the outdrive would only shift the RPM range that boat would pull to the left. I had it set so it would drive pretty straight at cruising speed - but at full throttle it would really want to pull. Would 1" off-center on a 7' wide hull cause this?

Thanks,
Tom