starboard starting problem?

[RICKEY]

instructions to start starboard 8V-71. step 1. remove lid from racor filter (that is mounted on the rear bulkhead app, 4-5" higher than the motor.) lift filter element out of canister, and wait for a large bubble too berp and come to the serface of whats left in the canister. (level drops down about two inches) replace element, and top off canister with clean fuel. check O-ring and replace lid. go topside to helm, hit the starter and off we go! now if I don't do this procedour the motor will start and run for app 2 mins, then the RPMs start droping slowly and then the motor stops completly. I then have to go through this whole bubble deal. the port side engine room racor is not mounted higher then the motor and when I hit the starter it lites right and humms perfect. all this happens when I let the motors sit without starting them over a period about a month. if I start them one a week I don't have this bubble problem. now Ive done a leak down test on all the fuel lines and returns. they are fine, haven't checked the engine canister yet for air leaks nor the fuel rails. was hoping someone could help before tearing into it. am I missing something?