I don't know anything about that motor,but in the sixties,my dad had a 65hp,from a good running tune to perfect tune,the boat speed would increase,30mph to 36mph.
First of all, you should have a tach installed. The main reason, to see what RPM the engine is running at with WOT. It could be that you're already achieving as much performance out of your engine as possible, as long as it's been installed professionally.
A few things contribute to how your engine will perform eg;
- Which prop you have installed.
- The mounting height of the engine.
- The offset of the engine.
- Regular servicing.
