went out last weekend with my 16' cape horn have a 2000 70 hp 4 stroke suzuki ran wot for 10 miles did some scalloping and starded back alarm came on temp light also rpms droped to 2500 or so. I stoped turned off engine restarted water stream was fine didnt seem hot went 6 miles or so same thing. new waterpump put in last dec has around 25 or so hours since.
Also keep in mind that the ECU can sense a rapid rise in temerature and set the alarm off before the engine actually overheats. It's refered to as a "gradient" temperature alarm. When you get the alarm, shut the engine of and restart it. If the alarm has stopped, then you had a "gradient" alarm. If it happens often than you have a t-stat or pressure relief valve problem. Also, if you're into a lot of seaweed, it can happen.