i take the approach of this...if it's an inboard set up,i use mercs.i like mercs,good guys wear black lol !!!i use strickly injected engines,because of their power delivery,smooth and crisp...fuel effiecincey,well,my sea craft gets in excess of 2nmpg,that's pretty good...
stern drive boats,they get what ever is in them,this boat had a older tbi volvo,it got a new mpi volvo...personally,i've had very few problems with both the merc engines and the volvo engines,i chose volvo diesels when i repowered my old bertram 31,these proved to be super reliable and fuel efficient too...