high rpm problem 70 hp 2 stroke new 2009

[newyam70]

problems all summer in and out of shop horn goes off finally broke down head for full cleaning and found no obstruction. NOW at full throttle 6000rpm my tach moves around from 5600 to 6000 with intermitent hesitations then at some horn will soun overheat. usually runs great at low rpm. engine is peeing real well at all speeds. thanks

[boats.net]

Probably needs new water pump and thermostats.

[newyam70]

yes

oh yes, did that as well