1992 150 hp outboard alarm issues help!!

this motor is on a 22 ft triton, this spring 1st time out when I ran 3000 rpm overheat alarm would sound motor would go into safe mode. turn off engine then could run all day 2900 rpm. read some posts talked to a boat guy. I replaced the cdi box. took boat out the following weekend ran full out 5200 rpm 14 miles up the lake and 14 miles back down the lake. no alarm no issues. next day put in got 100 yrd to the end of no wake zone hammered it 20 sec later overheat alarm..... shut down started back up could not run over 2300 rpm. alarm went off a lot that day and finally it would not start. put new impeller in and new thermostats. back to lake would run 3800 rpm before over heat alarm..... the next week installed new temp sensors one on each head. now I can run 4200 rpm as long as I want to. try 4500 and overheat alarm what doi replace now. I dot thinkit is overheating. help me lese

I had that problem on my Johnson and it turned out to be insulation on one the tan wires was worn thru and touching the engine block check your wires to be sure that's not it. Good luck

Check the motor temp with a temp gun to see what it actually is.