Help!!!! 2002 Mecury 50 hp 2cy 3 cyl- engine feels restricted/weak, runs great when choke is used

Here is the run down. 2002 Mercury 50hp 2stroke 3 cylinder model #1050412ZN. The engine will start relativley fine and will idle okay on muffs and on the water. On the water, while in gear under throttle the motor runs fairly smooth and sounds good, but it feels restriced and lacks power. This engine has an electric choke on the ignition. With the engine under WOT it runs feeling weak and restricted unless I activate the choke. If I constantly activate the choke, push the key in every 1.5-2seconds, the rpms ramp up, power is restored and runs as it should. I'm trying to figure out what the next step in my diagnosing should be.

The following things have been done in less than a month, and were all done before water testing. The same problem still occurs.

Carbs have been cleaned/rebuilt
New fuel tank, tank hose/bulb, new fuel line from tank hose to fuel pump, new fuel filter.
Fuel pump has been cleaned and rebuilt
Spark plugs have been inspected and cleaned.

I'm all out of ideas. Please help!!

If it runs better with choke then that clearly points to issues in the carburetors.------Perhaps you missed / overlooked something.

Agreed, and you'd better not keep on running it like that or you'll drill a piston.

If your boat has a built in fuel tank, look for a clogged anti-siphon valve at its outlet. Also, see if the vent system is open.

Jeff

And make sure that you don't have a vacuum leak somewhere that is leaning the mixture.

Check the fuel line as sounds like internal liner has degraded and restricting fuel flow. Have to cut the end off...

The fuel system/lines are all brand new from the tank up to the fuel pump. I didn't replace the lines from the pump to the carbs. They all looked and seem fine. But when I pull the carbs off again to re-rebuild them, I'll replace those lines too. I've heard of the "EPA" liner thing deteriorating on the fuel line from the tank to the engine, but mine is brand new. Do the other black hard rubber fuel lines do that too?

If lines are OK carbs need attention