Yamaha - Pilot Jet #53.8 Carburetor Fuel Metering Component 7CU-E4142-21-A0. Overview. Pilot jets are one of the first things I check when an engine won't idle right or feels sluggish off idle. Even a slight blockage or the wrong size can throw everything off at low speeds. I've seen engines come back to life just from swapping in the correct jet. When it's right, the motor idles clean and transitions smoothly into throttle without hesitation.. Key Features. • Low-Speed Fuel Regulation - Controls fuel delivery at idle and low throttle for smooth operation.• Precision Jet Sizing - Calibrated at 53.8 for accurate fuel-air mixture in carbureted engines.• OEM Thread and Fit - Installs directly into the carburetor with proper seating and alignment.• Improves Throttle Transition - Helps eliminate hesitation when moving from idle to acceleration.. Engine & Boat Compatibility. Designed for Yamaha outboard engines equipped with carbureted fuel systems that utilize a pilot jet for low-speed fuel