I have a 2007 5.7 Mercruiser At 3200 RPM it runs perfectly for 20 minutes then starts to misfire. It feels as if it is being fuel starved. I ran the engine and removed the air cleaner / flame arrester and looked down the chokes of the twin barrel. The port side choke looked normal but the starboard choke the fuel was not a steady stream it was spurting. During the problem I have removed the gas tank cap in order to prove it is not a plugged vent problem. The engine noise changes as this problem happens, it sounds almost like sticking lifters but I'm not sure.This can be reproduced as often as required and is always the same within a minute or so. The engine has about 90 hours on it and has just been fitted with a new carb (When I purchased the boat the engine rebuild had been completed with an automotive carb).
