Guys I have a 01 Mercury 225 EFI that runs like a champ until I get to WOT and it starts beeping. I back off a bit and it runs fine. Any idea what that may be?

Usually you're losing water pressure.
Is it a solid tone or not?
If it is it's getting hot.
If not, you've probably got a little air in the oil tank and the float is bouncing around.

Thanks for the feedback! It's not a solid tone although I will check the thermostats and impeller. (Just bought the motor) just to be on the safe side.

You've probably got a little gap in your oil tank, when you trim it out enough it shakes the float, that's all it needs to start squawking at you.

Sounds like it might be hitting the rev limiter. I think it�s around 5850 rpms.

Some good points above from educated guys. Heat if solid. Oil if not, screw off your oil cap on the motor while idling on the hose or something and let the oil level rise back up. Then screw back on. Or very well could be rev limiter, don't doubt that. I had a motor one time doing the same thing on a Bullet because it was all over the rev limiter.

That's what it was, air in the oil reservoir. Runs like a champ. Thanks for your help guys!