I got a bit more info that I'll document here.
The injector pump
is a PS61/850/4/2750
and as noted the 61 represent the total fuel
pumped in cm^3 but here is the additional details. That is 61 cm^3 in 1000 squirts at 850 RPM. The 4 is the governor spring location and 2750 is the max no load RPM.
My engine would only rev to 2250 max RPM unloaded and the other day it would only go to 2000 RPM.
It turns out that the air cleaner (if you can call it that) was restricting air flow. Lots of gunk clogging the holes. That was cleaned up with some carb spray and we are back to 2250 RPM.
manual indicated that General Vehicle use has a rating of 82 hp at 2800 RPM, Industrial is 81 hp at 2600 RPM and Heavy Duty use is 72 hp at 2200 RPM
SO the injector pump
rating indicates a max RPM of 2750. The throttle lever on the pump is wired in place to limit the maximum RPM.
I am guessing that Perkins put in injector pumps that were rated to go to 2750 (2800) RPM and then wired the throttle stop to a max RPM to suit the service. Heavy Duty for a sailboat engine at 2250.
This suggests that you could change the throttle stop and increase the actual max RPM up to the max rated RPM stamped on the fuel injector pump.
That or I've got a problem with one or more of the injectors or the pump.
Sometime this summer I'll have the injectors rebuilt and that will tell us if it is the injectors.
The engine runs smoothly so I suspect that there is no problem with the injectors....