1 - Buy an infrared temperature gauge from Harbor Freight for like $10.
2 - Point it at the radiator hose fitting (metal part) at the top of the engine. This will give you engine outlet temp. Compare to gauge and rule out gauge problem.
3 - Point the gauge at the inlet fitting at the top of the radiator (metal part) - this is the inlet temp to the radiator.
4 - Point the gauge at the outlet fitting at the bottom of the radiator (metal part) - this is the outlet temp to the engine. The temperature drop should be anywhere from 30-60*F. If you are not getting this kind of temp drop then you have a radiator cooling problem.
I could speculate at top issues but we need to know if this is really overheating or not. Here is about the "most" to "least" likely...
1 - Cooling system contamination - flush and fill never happening, sludge build up - low temp drop in radiator
2 - Bad thermostat - probable direct overheat/overflow
3 - Electric fans not cycling - low temp drop in radiator
4 - Head gasket or head failure - oil in water or water in oil
5 - Other engine failure
6 - Some change to radiator/engine shrouding that changed airflow through radiator.