2001 4.3L mercruiser temperature intermittent alarm, moslty at higher rpms. Replaced impeller in foot last week. Replace thermostat last season. Noticed Starboard manifold hot and thermostat and port side manifold cool. Removed and cleaned manifold and elbow. Cleared some metal, and all water channels are clear. Starboard side still hot. Should one side be hotter than the other? I'm thinking about running test without thermostat to see if thermostat is not feeding water to starboard sie. Any ideas? Thanks.