I've got a 1989 Mariner 4cyl Magnum on a 15'5" Peterbourgh aluminium boat. It revs 5400 at WOT and goes 26 mph with good hole shot at medium load. It seems to cruise nice at 4200 rpm at 18 mph. At this point I can do two things without seeming to alter rpm or speed. I can tilt up and have a 3'prop spray to starboard or down and get rid of spray. Which trimming is proper for engine performance and fuel econemy.Does the boat and engine seem to be proped up right or is there somthing I can try for more speed.
