98 115 alarm help

[sneak attach]

While we were out yesterday I went to pull in a cove and ran on a submerged tree stump centering the hull of our 18' Hurricane. After getting off the tree we headed back and a buzzer went off "after reading it sounds like the overheat alarm, never had a motor with warning alarms" the boat only ran smooth around 2000 rpm. Made it back to the ramp and I kept a check on the pee stream which looked fine all the way back. When I restarted to load the boat the motor cranked and idled fine until I bumped the throttle to push it the rest of the way on the trailer at which point it died. When I got it back I put the ears on, good stream but just not running quite right, a little rough. I did notice I lost my trim fin off the motor.

The motor was just serviced a few weeks ago with a new impeller put in. Any advice or ideas would be appreciated.

[boats.net]

Need to have compression test run on it. Could have low oil or overheat warning, in either case not good to continue running with alarm going off.Check oil level on engine oil tank to see if low, below lower line on oil tank. Remove lower unit and check water pump.

[sneak attach]

update

I took the boat back to the dealer who ran it and could not duplicate the problem. He checked the engine and everything was ok. I took it out today and after about 8 miles the alarm went off again we were right at a marina so I pulled in and let it cool she started up and I ran her back to the ramp staying around 3500 rmp wiith no alarm however if I dropped her to 2000 rpm she died then started back but has a low rpm dead spot. The alarm seems to only go off if I run her over 4500 rpm for a few miles. Guess I'll take her back tomorrow.

[boats.net]

Probably overheating, check water pump housing and impeller, thermostats and pressure control valve.

[amlorenz]

Maybe sucked some sediment up into the intake if you were running it shallow. Could try backflushing the motor with a hose and see if you push anything out. Happened to me one time and this fixed it.