Who has a 20 I/O?

[Shadetree]

Just wondering what kind of performance other folks are seeing on the 20 cc with the Merc 120/140 I/O setup. Banedog's 1970 has this setup(we think!)- the 4 cyl gm has had a valve cover swap, and we can't tell for sure what the displacement is without pulling the head and checking bore/stroke(no thanks!) I'm also pretty sure that the wrong drive ratio is in this boat, should be 2:1, I think it's more like 1.6:1, and I think it's over propped as well, came with a 13.75x21. Boat runs happily at 3000 rpm at about 24 mph, but maxes out at 3800 rpm. Book says it should run 4200-4600 w.o.t. Throttle plates are wide open @ full throttle. Timing is set to factory specs, no pinging, no overheating. I think the little 4 is tired, and have recomended a 3000rpm redline for longevity. We're gonna run the boat tomorrow with a 14x19 stainless prop, and see what it does. Anybody else have any thoughts or ideas?
Thanks,
Pat in MD