If you don't already have a failsafe I'd recommend getting one of these: [link=http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXJTW3&P=ML]Venom Smart temp[/link]
It doubles as a fail safe and a temp gauge. If you're engine starts to overheat it'll automatically slow you down so you don't end up cooking the thing.

If you do have one already just go with an infrared temp gun or an onboard unit.
[link=http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXHEM4&P=ML]Onboard[/link]
[link=http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXEMG5&P=ML]Infrared[/link]

Oh and in my professional opinion i think 285.63 is way too hot to be running your engine. I'd go no more than 285.32 just to be on the safe side.