mercury optimax 150 hp ob 2006

won't run off idle or under 2500 rpm, warning buzzer sounds and rpm drops to idle, throttle back to clear buzzer and go wfo runs fine above 2500 rpm
if i can get it there any ideas ? ps. starts easy and idles fine good to go at no wake speed

There is only three things that would cause the guardian system to restrict rpms from the 2500 rpm range -

1) electrical problem with the oil pump

2) no/low oil flow

3) overheat

A fourth option could be a bad sensor indicating an "overspeed" condition.

The first 3 are baaaaaad things and could kill your engine.

Take it to a dealer and have it hooked up to a DDT (diagnostic terminal). It will tell you what is causing the alarm.

We can "guess" all day at possible causes but one of the downsides of the very hi-tech Opti's is that you need a specialized computer to troubleshoot them. The technology that allows them to run makes the engine in your car look like something you would find under the hood of Fred Flintstones wagon in comparison.