whats the biggest engine u have seen on a 21' Flatscat?

I am looking at replacing the Yamaha 150max on my 21' Flatscat with a 250SHO W/TRP lower unit. Yes I know the flatscat only rated to a 150. I have heard about guys running bigger that the 150 and I wanted to know how the boat performed with the bigger engine.

whats the biggest engine u have seen on a 21' Flatscat?