90 2 stroke- overheat alarm-did the common

[hiflutin]

Late 90's 90 2 stroke,
Idle's fine,
pee's good,
throws overheat alarm when I run 3800 rpm for 10 min,
Put new
Impeller kit
Thermostat
Temp sending sensor/switch

What do I try next

Thanks

[rodbolt17]

most likely.
now you get to pull the cyl head and cover.
scrape out all the scale.
reassemble.