We had a similar problem this spring with the 150 HPDIs during the first run. Last fall, I removed the secondary fuel filters (white/clear plastic fuel strainers), cleaned them then reinstalled. I am fairly certain the EFIs have a similar arangement. During spring start up, the motors would run for about 10 minutes and eventually sputter and stall. I went to the Yami dealer and asked for new O rings for the strainer and explained the situation. Yami tech says that the ethanol has swelled the plastic strainer and will not allow it to seal properly. The fix is to drain the fuel from the strainer and allow it to dry out for about 30 minutes or more. Well about 35 minutes later the strainer popped back into the housing and presto, no more lost power or soft primer bulb. Other problems could be a minor air leak in the fuel system prior to the fuel pump on the motor that may not be indicated by fuel leaking. The pumps work by vacuum and if there is an air leak you will loose vacuum pressure in the fuel line and starve the engine. Check the primary fuel filters (racor or Yami water separators) but if you messed with the secondary filters this is probably where the problem is. I had to squeeze the bowl hard to force it up into the housing and the castle nut will turn untill there are no more threads showing. Don't drop the lock spring into the water as they are $15.00. Don't ask me khow I now this.
