703 controller on a 1985 70 Hp yamaha

Took the above mentioned off an old boat and installed it on my 16' sea ark. The fish/ski boat it was on originally had trim, oil,tach gauges that I don't want in my sea ark. We installed the 703 controller and the 70 Hp motor and tested it with earmuffs with no problems. Put the boat in the river to test run and after only a few minutes at 1/4 throttle the 703 started making a continuos buzzing noise. The oil level is fine and the motor was pissing strong... Then after a moment at full throttle ( buzzer still sounding) the motor cut back to idle and shaking wildly... The buzzer would not stop and the motor would not go above the shaky idle. What is the buzzer alarming and is that what's causing it to not run above idle. Any help would be great! Thanks

Re: 703 controller on a 1985 70 Hp yamaha

One of two things. Low oil tank alarm or more than likely an overheat. Motor will automatically cut back to low RPMs to help save the motor but give you enough power to stay out of trouble like being in a busy dangerous inlet. FRED