The current 2" pipe rises to 3 ft above the waterline near centerline, then drops through a swan neck to about a foot above WL

The discharge is through a 2" nipple welded to the aluminium hull.
Changing all that to 3" is a major project
Given that Yanmar has the same 3" exhaust (actually 76mm) exhaust for the entire JH range from 39 to 125 HP, I am hoping that they will agree to warranty their engine with my 2" system.
I have seen a 3" system reducing to 2" on the 53 HP Yanmar, but not an entire 2" system
I would like to hear of one
Our waterlift is much larger than Yanmar's