This boat would start without any trouble, but at full throttle it would starve of fuel and stall. The inner lining of the old fuel lines had broken up into rings, which came away, flowed down the line and blocked the fuel flow. The pieces showed up in the clear fuel filter, which is how I knew something was going on.

Ethanol in the fuel and sun on the outside both break fuel lines down, so replace any line that's cracked or brittle. I cut the new line square with hose cutters, and clamp it with stainless steel clamps whose slots are pressed rather than cut through, so they don't cut into the hose.