Sounds very much like timing to me. In most newer marine applications the gears are 100% strength in forward and reverse- so it's the gears which change the rotation of the propshaft. The starboard prop turns clockwise from the stern view; the port CCW. Obviously from the helm the controls are set properly. Your best bet is find the compentent local MB independent mechanic and ask him to check the engine out after finding out as much as you can here. Why is the IP different than the Bosch found on automotive applications so that you can't do a drip test? BTW your engine is called a OM616. What is the HP- 67? That's standard for the engine.