1999 Mercury 25 HP 4 stroke alarm and cutting out

by Geoff

Iam having problems with my 1999 Mercury 25HP 4 stroke and I am hoping someone can help me. I purchased this boat yesterday and the motor worked as it should but only while on low idle. I took it out for the first time today and when it was used near the top end of its speed range the motor alarm came on and basically bogged the motor down. I assumed it was a high temp alarm so I shut it down. This happened a couple of time and I tried to trouble shoot it. Oil is good, water is flowing out the "pee" hole and everything seems normal to me. Any troubleshooting steps I should take to try and figure this out?

Thanks for the help

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