Evinrude 120 hp overheating signal

[Garyiam]

I bought a used boat and did have a mechanic do some initial maintenance. He changed the prop, throttle control, and impeller. On the first outing and after a couple hours of use i was doing about 25 mph. The boat shut off and the continuous overhead alarm sound came on. After sitting a few minutes the boat started in reduced power mode. When I got back to the boat trailer I decided to switch off the battery to see if it would reset. After turning the battery shut off back on the boat started up easily and without a warning tone. When this all occurred I had a half tank of 93 octane ethinol free gas and a half tank of oil. I took the boat out on two seperate occasions later and all went well, but this weekend the boat alarm for overheat when off doing about 25 mph. The water from the pee hole is hot, but will not burn you when your hand is under it. Is this a temperature sensor issue. There are two on the boat and one is quite pricy. How do I determine if they are the issue, and if so which is the failing sensor. I have an Evinrude 120 hp motor, VE120TXESB.