need help bad

i have a 02 civic ex110K, Radiator1 yr old new waterpump and timing belt 1 mo old,All hoses checked for leaks I live in hawaii and my mechanic said no need for a thermostat so i said take it out thus no thermostat. Radiator 50/50 h2o and rad fluid..He has looked it over 3-3 x but it keeps overheating. If in stay under 60mph it goes 1/8 "under middle on gauge.Before i had this problem it was always at 25% or less from cold.I drive 43 miles to work first 12 are 35mph no problem..Then next approx.31 are highway speed limit 55-60.When i go 70 it overheats in seconds. As long as i stay around 55-60 it is ok but if there is a traffic jam or backup it will overheat in minutes. i thus must turn it off when ever i can in the traffic to cool and cars in back do not like that.Can anyone tell me what more i can do to stop the overheating.. I am at my wits end. All hoses are good as is circulation and there are no leaks. My A/C is broken so do not use that and when i run the heater it at times will bring it down maybe 1/8" but very little and dammit it is hot overhere and by the time i get to work i am a sweatball with the heater running for 1 hour..Thank you for any help you can give me as my mechanic cannot think of anything else..I noticed the ECD light comes on once in a while could that be any thing with it..We have no emmission control checks here in hawaii so i dont care to get it replaced if it goes.Thank you again for any help:crying: