GP396

Although this is not a vintage site I thought I'd post this question here in hopes of finding someone with info/knowledge of old Yamaha's.

I recently purchased a 71 GP396. Engine runs great but it was bogging at takeoff. I've since replaced the primary and secondary springs with similiar springs (still looking for original). I'ts now much better but I would like to know at what RPM should I get clutch engagement and what should my max RPM be at full throttle. Spec indicates 28 hp at 5500 RPM. Does this mean I should not see more than 5500 RPM at full throttle?

Any help is appreciated.