Yamaha 150 Running Poorly

[Paul Southway]

I have a Yamaha 150 Outboard TXRC, a 2004, 2 stroke. Was running great until this Spring when we detected a noticeable lack of power at higher RPM's and hesitation when we tried to give it more gas. Before this, she ran smooth and cruised nicely at about 3500 RPM's. Now, it seems pokey at 3500, and when I lean on the throttle, it immediately hesitates, after which it will kick in. After a 45 minute run, the other day, it wouldn't even idle well, stalling - restarting - stalling back to the slip. I put a Micron 10 filter on last month hoping it was water in the fuel and have changed the plugs and fuel filter in the engine compartment. No visible signs of problems, stress, water, or dirt. Have not noticed the squeeze ball collapsing, or any kinks in the fuel line.

I like to get an opinion on what to go after next.