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Writer's pictureMike Hill

The Evolution of the Mercury 2-stroke V6 Outboard carburetor

Updated: Oct 6


The history of Mercury 2-stroke outboard carburetors, specifically the transition between the WH, WMH, and WMV series, reflects the evolution of carburetion technology aimed at enhancing engine performance, efficiency, and reliability.


1. WH Series Carburetors:


Introduction and Features: The WH series, introduced in the late 1970s and early 1980s, was known for its "Wide Horn" design, which allowed for greater air intake and improved fuel-air mixing. These carburetors were commonly used in high-performance and racing engines, particularly in Mercury's V6 models. The WH carburetors featured multiple venturis and larger throttle bores, enabling more precise fuel metering and higher power output.


Applications: They were widely used in high-performance outboards such as the SST-140, SST-120, F1 / F200 tunnel boat and Pro Carb drag race classes, favored by enthusiasts and racers for their ability to provide a rich fuel mixture necessary for maximizing power.


2. WMH Series Carburetors:


Development and Design Changes: The WMH series succeeded the WH series and was introduced in the late 1980s and early 1990s. This series featured a more compact design and refined 3-stage fuel metering systems. The WMH carburetors aimed to improve fuel efficiency and reduce emissions while maintaining performance.


Technological Advancements: The WMH carburetors incorporated advances in carburetor technology, such as improved float and needle designs, which enhanced fuel flow control. They also featured better atomization of fuel, contributing to more efficient combustion.


Usage: While orignal found on the the 2.5 Liter 150, 175, 200 and 245 HP outboards, they are still used in performance and drag race applications, the WMH series was also found in a broader range of outboard engines, including those designed for recreational use.


3. WMV Series Carburetors:


Introduction and Characteristics: The WMV series represented further refinement in carburetor technology. Introduced in the mid-1990s, these carburetors focused on meeting stricter environmental regulations by reducing emissions and improving fuel economy. The WMV carburetors featured even more precise fuel metering and better control over air-fuel mixtures across different engine speeds and loads.


Emission Standards and Efficiency: The development of the WMV series was driven by the need to comply with increasingly stringent emission standards. These carburetors were designed to optimize the air-fuel mixture for cleaner combustion, thus reducing pollutants like hydrocarbons and carbon monoxide.


Wider Application: The WMV series was used across a range of Mercury 2-stroke outboards, including the SSt-120, from small engines to larger 3.0 Liters, high-output models, reflecting a shift towards more environmentally friendly and fuel-efficient designs.


Transition to Modern Fuel Systems:


The introduction of electronic fuel injection (EFI) and direct fuel injection (DFI) systems marked the end of the carburetor era for Mercury's 2-stroke outboards. These systems offered superior fuel management, better performance, and significantly reduced emissions. EFI and DFI systems could precisely control the amount of fuel injected into the combustion chamber, leading to more efficient combustion and cleaner engine operation.


Legacy:


The WH, WMH, and WMV series carburetors represent significant milestones in the evolution of Mercury's 2-stroke outboard engines. Each series reflected the technological advancements and regulatory changes of its time, pushing the boundaries of performance and efficiency.


Today, while these carburetors are largely replaced by more modern fuel injection systems, they are still valued by collectors and performance enthusiasts for not only their role in the history of marine engines but also the price point of building fast and reliable powerhead.


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