Engine Conversion Possibilities for the Bobcat 742B

[MikePhua]

The Bobcat 742B and Its Historical Footprint
The Bobcat 742B skid steer loader was introduced in the mid-1980s as part of Bobcat’s push to expand its compact equipment lineup. Manufactured by Melroe Company, which later became Bobcat Company under Ingersoll Rand and eventually Doosan, the 742B was designed for versatility in landscaping, agriculture, and light construction. It featured a Ford industrial engine, typically the 1.6L gasoline variant, paired with a hydrostatic transmission and chain-driven final drives.
By the early 1990s, Bobcat had sold tens of thousands of 700-series loaders globally, with the 742B becoming a favorite among small contractors and rental fleets due to its simplicity and ease of maintenance. Its compact footprint, weighing around 4,800 pounds, allowed it to operate in tight spaces while still delivering over 1,200 pounds of rated operating capacity.
Terminology Annotation

• Skid Steer Loader: A compact, rigid-frame machine with lift arms used for digging, grading, and material handling.
  
• Hydrostatic Transmission: A system using hydraulic fluid to transfer power from the engine to the wheels, allowing variable speed control.
  
• Engine Conversion: The process of replacing the original engine with a different powerplant, often for performance, reliability, or parts availability.
  

Why Consider an Engine Swap
Owners of aging Bobcat 742B units often face challenges sourcing parts for the original Ford engine. Common issues include:

• Cracked cylinder heads due to overheating.
  
• Carburetor wear and fuel delivery inconsistencies.
  
• Difficulty finding ignition components and gaskets.
  

In some cases, the cost of rebuilding the original engine exceeds the value of the machine, prompting owners to consider alternative powerplants. Engine swaps can breathe new life into these loaders, especially when paired with modern fuel injection and improved cooling systems.
Popular Replacement Options
Several engines have been successfully retrofitted into the 742B chassis, including:

• Kubota V2203: A 2.2L diesel engine known for reliability and cold-start performance.
  
• Honda GX690: A 22 HP air-cooled V-twin, suitable for light-duty applications.
  
• Perkins 403D-15: A compact 1.5L diesel with low emissions and good torque.
  

Each option requires custom mounts, adapter plates, and attention to cooling and exhaust routing. The Kubota diesel, for example, offers better fuel economy and torque than the original Ford engine but may require frame modifications to accommodate the radiator and fan shroud.
Electrical and Hydraulic Integration
Swapping engines isn’t just about bolting in a new block. Electrical compatibility is crucial. The original Ford engine used a 12V system with mechanical gauges. Modern engines often include electronic sensors and ECUs (Engine Control Units), requiring rewiring or gauge replacement.
Hydraulic pump alignment is another critical factor. The 742B uses a belt-driven pump mounted to the engine crankshaft. Any replacement engine must match the pulley alignment and rotational direction. Failure to do so can result in cavitation, overheating, or pump failure.
Cooling System Considerations
The original radiator on the 742B was sized for the Ford engine’s thermal output. Diesel engines typically run hotter and require more airflow. Upgrading to a larger radiator or adding an auxiliary fan may be necessary. In one case from rural Montana, a Kubota-powered 742B overheated during summer grading work until the owner installed a dual-fan setup with a thermostatic switch.
Fuel System Modifications
Switching from gasoline to diesel requires replacing the fuel tank, lines, and filters. Diesel fuel systems operate at higher pressures and require water separators to prevent injector damage. Additionally, diesel engines often need glow plug circuits or intake heaters for cold starts.
Legal and Safety Implications
Engine conversions must comply with local emissions and safety regulations. In California, for example, off-road equipment is subject to strict diesel particulate standards. Some municipalities require inspection and documentation of engine swaps, especially for commercial use.
Safety tips include:

• Installing heat shields around the exhaust manifold.
  
• Verifying throttle linkage compatibility.
  
• Ensuring proper grounding and fuse protection.
  

Anecdote from the Field
In 2021, a landscape contractor in Ontario retrofitted his 742B with a Kubota V2003 engine salvaged from a generator. After fabricating custom mounts and adapting the hydraulic pump, the loader returned to service with improved fuel economy and quieter operation. The project cost under $2,500 and extended the machine’s life by at least five years.
Recommendations for Conversion Projects

• Choose an engine with similar or greater torque output than the original.
  
• Verify crankshaft rotation direction and pulley alignment.
  
• Upgrade cooling and fuel systems to match engine requirements.
  
• Document all modifications for future service and resale.
  
• Consult with local authorities regarding emissions compliance.
  

Closing Reflections
The Bobcat 742B remains a durable and capable machine, even decades after its release. While its original Ford engine may be showing its age, thoughtful engine conversions can restore performance and reliability. With careful planning, mechanical skill, and attention to integration details, owners can transform their aging skid steers into modern workhorses—ready for another generation of digging, hauling, and grading.