^^^ That that right there is what I would go with. At full throttle, it's not uncommon to get air bubbles across the transducer and it will sound off. A couple of other engine related things are: Knock sensor, engine temp, oil pressure, water flow, may be fuel temp.
What engine do you have? The Marine Power may have 2 oil senders, one for the gauge, one for the sounder. If the oild level is too high, the oil will foam up and cause the sounder to go off even though the gauge says the pressure is normal.