1991 45" Viking aft rail question

I ran one 45' with them, had 6v71's and ran well. I do not know if the lift rails were the reason why......

What are "lift rails"?

Like a spray rail, but they're alongside the hull on the edge where the hull meets the hull side. Kind of concaves downward a bit. Some manufacturers added them at the factory to fix a hull design that didn't run as stable as expected at cruise speeds.

Like this:
48rollchock-jpg.77029 (800×600) (yachtforums.com)

Oh ok. The way it was phrased I thought the OP was referring to something with the motor. Spray rails are common, but I can't see them having much effect on lift, no matter how angled, over what the trim tabs and chines designed for the hull do.

I notice that they help with stability and lift also......

I owned a 1989 Viking, what is happening t0 make you want to add lift rails.