Custom replacement idle air jets are now available for Mercury WH-series carburetors commonly found on Mercury V6 2-stroke outboard engines, specifically the 2.0-liter and 2.4-liter powerheads, as well as the high-performance or race-modified 2.5-liter configurations. T
 
hese jets are engineered for precision air metering, essential in maintaining stable idle and crisp throttle response across varying engine loads and environmental conditions.
 
Idle air jets in the WH-series carburetors control the air bleed to the idle fuel circuit, significantly influencing the idle air/fuel mixture. In this system, larger air jet sizes correspond to a leaner idle mixture due to increased airflow through the idle circuit. These jets are a critical component for tuners adjusting idle characteristics in both stock and modified Mercury V6 outboards.
 
River and Race Idle Jets
The 46 jet (0.046" diameter), Mercury part number 1399-5317, is commonly used in baseline configurations requiring richer idle air mixtures.
 
The 48 jet (0.048" diameter), part number 1395-6246, allows for a slightly leaner mixture and is suitable for moderate tuning adjustments.
 
The 50 jet (0.050" diameter), Mercury part number 1395-6028, delivers a balanced air/fuel idle ratio and is often selected for general performance applications.
 
For tuners seeking leaner idle conditions, the 52 jet (0.052" diameter), part number 1395-6359, and the 54 jet (0.054" diameter), part number 1399-5225, provide increased air metering capacity.
 
These sizes are frequently used in racing setups or high-altitude environments where air density and engine modifications require more air in the idle circuit to maintain combustion efficiency.
 
Drag Race Idle Jets
For applications involving drag racing or aggressive holeshot strategies, even leaner air jets are necessary to reduce low-end fuel loading and improve throttle snap during staging procedures.
 
Larger (leaner) air jets are available in 0.068-inch (Mercury P/N 1395-6029), 0.074-inch (Mercury P/N 1399-3794),0.074-inch (Mercury P/N 1399-3794), 0.076-inch (P/N 1399-3796), and 0.078-inch (P/N 1395-6680) diameters.
 
These sizes are particularly relevant for racers employing a 7–10 mph rolling idle approach on a starting barge, where clearing excess fuel from the idle circuit before the green flag provides a cleaner, faster launch.
 
Each jet is CNC-machined from marine-grade brass to ensure dimensional accuracy and corrosion resistance. Flow characteristics are verified post-manufacturing to ensure that each jet size performs consistently within its specification range.
 
The idle circuit in Mercury WH-series carbs demands tight control over air delivery, especially when paired with modified port timing, aftermarket reeds, or non-standard exhaust configurations.
 
Tuning these idle air jets should be done in conjunction with adjustments to the idle timing and consideration to the main jets. Proper throttle arm synchronization of the WH-series carburetors is also essential to achieve uniform idle quality across all cylinders in multi-carb setups, such as those on Mercury 2.5L V6 race builds.
 
Our jet offerings cover key OEM Mercury part numbers with direct-flow equivalents.
 
Includes six (6) Idle Jets for the Mercury WH Series Carbs.
 
Contact mike@buckshotracing77.com or +1-714-697-1716 with any questions.