oil not pumping from tank in the boat up to the motor

I have a 2004 200 ox66 that is not oiling the way it should from one tank to the other. Last year I had a problem with this in the summer so I cleaned the filters made sure that the hose was not kinked and every thing has worked fine until now. Yesterday I ran about 40 miles no problem, today I ran about 6 miles and ran low of oil. When I run all of the oil out of the tank and the oil level guage gets low enough it will sound the alarm and I can take the cowling off and turn the key and fill the tank manually by flipping the switch, but cant figure out why sometimes it will fill the tank and sometimes it dosent. any ideas?

Tony