Don't have much time now , but will try to relay my experience
number of years ago with my 3GM.
Same exact systems, would run all day if motoring...as soon as I sailed with more than say 10 degree heel (either starboard or port tac) motor would run for 10-15 minutes and quit. Would
bleed and then would run again no problem.
I had a few well respected mechanics go over and change whatever they felt needed changing after I had taken my best
shot...no one found problem...never found out what it was but
wound up changing all fuel del. system including fuel filter
, fuel pump
, entire racor
unit and all hoses and fittings The only thing
original was the fuel tank
Hopefully your situation will not be such an adventure.
I started by bypassing different filters by using a day tank (small aux. tank) and fuel line, the ones with the rubber bulb.
(rubber bulb good idea to install in line as will help when bleeding system even after problem solved
And then tried bypassing different filters and fittings...you get the idea. Took me 2 years and never found specific problem.
As you have to bleed the system more often you must be aware
that you can actually cause more air leaks
as there are some copper washers (i think in the 2nd fuel filter) that are recommended by changed out. Will try to remember more and post when time allows.
Have kept daytank until recently as was always good for keeping a few extra gallons of clean fuel if conditions stirred up the nasties in the main tank.
Hope this helps.