I have a pair of 2003 Mercury 200 EFIs on a 31’ center console, they have about 425 hours. When I first fire them up they run great, boat jumps on plane real quick no issues. After they run for awhile especially at idle or trolling speed they will be down on power and the boat struggles to get on plane. Once up on plane it seems like they run back to normal but getting them up is difficult.

I have hooked the motors up to my ddt and there are no trouble codes and I cannot find any other issues. Does anyone have any ideas why these engines are doing this? I don’t think the boat is overpropped since it hops up on plane no problem when motors are cold.

Any help is appreciated.