2001 225 ficht "no oil"
 

I have a 2001 ficht 225 and the no oil alarm is going off. The tank is full
and when I disconnect the oil supply line at the motor there is lots of oil
when I squeeze the primer bulb at the tank. The alarm sounds and then I shut
down the motor and restart and can drive for a few minutes then it sounds
again. I have since drove for 20 minutes near full throttle and no alarm.
What should I look for. The service manual says to check for an oil pressure
of 6-20psi at the switch. I did that and consistently get 20 psi. Thanks