2002 mercury 30hp 4stroke alarm at high speed

[LuckyGravz]

Hi, my 2002 mercury 30hp outboard 4 stroke started on alarm while I had it out yesterday, alarm only comes on at close to full throttle. Tried again at hove with water muffles and it's doing the same thing, any clues as to root cause?

 

[QBhoy]

Oh jeez.

Im not one for preaching but maybe you shouldn’t run it full throttle on the hose. Not usually a good idea.
Anyway...two main causes for an alarm at a guess

Its over revving and alarming at the limiter (where my money is)

its overheating on the muffs and not getting enough water to cool at those revs.

watching it again. It’s 99% alarming because the engine it at the rpm limiter. I can hear it.
if it does this in the water under way...you are under propped.

Steady as she goes maybe. All the best.