here is one source..........regardless of what others had suggested don't rebuild another motor........
And throttle plates must be wide open.
I have a Mercury 6hp 4-stroke, my2005. This motor also comes in Mariner, Tohatsu and Nissan "costume", afaik.
from memory, cruise 3500, WOT 4600
re: " work harder than it should..." What RPMs do you normally cruise at? What is your RPMs @ wide open throttle?