1989 mariner 115 straight 6 starts fine when cold - but then struggles to start and idle as motor heats up during the day. It also struggles to get over 2000 revs ie move from 2 to 6 cyclinders when the power is on. A quick push on the choke seems to remedy this and the motor then revs up. Water coming out the tell tale is not overly hot.I have replaced stator. serviced carbs. checked fuel line for air leaks. replaced diaphram on fuel pump - but there may be an issue with the values in the fuel pump?