200 salt water series problem

i have a 1997 yamaha 200 salt water series that started giving me problems last june and i havent been able to mess with it since last summer before this started the motor ran fine all its life with zero problems. my original problem that started was if i ran any higher than 4500 rpms the motor would shut down into safe mode and drop to 700 rpms. long solid beep. either oil or water. ran it with the cowling off and same thing and the reservoir on motor had full tank. so had to be temp. long story short this is what i changed out so far. complete water pump, all 3 temp sensors and both thermostats. i took the head covers off and had little build up but i cleaned anyway. they are spotless now. i even changed the oil sender in the motor tank to make sure it wasnt sending a bad signal. i still have the same problem. i can start the motor up and take off from the landing and it will run at 5600 for about ten seconds then shut down. i take the cowling off and i can put my face on the block its so cool. so i figured it was electrical so i went through the whole wire harness and found no shorts or loose wires. so then i went buy a new 703 control box and hooked it up and the motor started acting even stranger. giving throttle the motor would jump and fluctuate rpms and runs good then runs and sputters like dirty carbs but the carbs are clean. only thing i can think of is the cdi has a short in it or just is going out and wondering if anyone on here ever had this issue and have something i didnt do before i go spend 800 on a cdi. thanks. mike

wp gauge

also i do have a wp gauge and im getting 25 wot, 10 idle

[Brisco58]

I had a very similar problem with my 1998 150 VMAX. J had changed the pump and thermostats and checked the switches. I was getting ready to pull the heads when I read that the PRV could be causing the issues. I changed the PRV and put in the new version and I have had no issues since. It looked like it was stuck open so I would assume it was dumping cooling water and causing the engine to overheat at higher speeds. I don't know if you have changed the PRV yer, but If you haven't give it a try. It only costs a few bucks.