Engine Swap Challenges and Solutions on the Bobcat 751 Skid Steer

[MikePhua]

The Bobcat 751 and Its Powertrain Evolution
The Bobcat 751 skid steer loader was introduced in the early 1990s as part of Bobcat’s compact equipment lineup, designed for landscaping, light construction, and agricultural tasks. With an operating weight of around 2,400 kg and a rated operating capacity of 680 kg, the 751 was powered by a 1.7-liter Kubota V1702 diesel engine producing approximately 36 horsepower. This engine was known for its reliability and simplicity, but after decades of service, many units now face engine fatigue, cracked blocks, or oil consumption issues—prompting owners to consider engine swaps.
Bobcat, originally founded in North Dakota in the 1950s, became synonymous with the skid steer concept. The 751 was one of its most widely sold models during the 1990s, with thousands still in operation globally. Its compact frame and mechanical layout make it a candidate for engine replacement, but not without complications.
Terminology Annotation

• Engine Swap: The process of replacing a machine’s original engine with a new or different model.
  
• Bellhousing: The casing that connects the engine to the hydrostatic transmission.
  
• Mounting Plate: A structural bracket used to secure the engine to the loader frame.
  
• Flywheel Coupler: A flexible joint that transmits torque from the engine to the hydraulic pump.
  
• Governor Linkage: A mechanical system that regulates engine speed based on load.
  

Common Reasons for Engine Replacement
Operators may choose to swap the engine due to:

• Cracked block from freeze damage.
  
• Worn piston rings causing blow-by and oil loss.
  
• Failed head gasket leading to coolant contamination.
  
• Lack of parts availability for older Kubota models.
  

In one case, a 751 used for snow removal in Ontario suffered a cracked block after a winter cold snap. The owner had neglected to use antifreeze, and the resulting damage made repair uneconomical.
Engine Options and Compatibility Considerations
The original Kubota V1702 is no longer in production, but several alternatives exist:

• Kubota V2203: A newer 2.2-liter engine with similar mounting points but different intake and exhaust routing.
  
• Perkins 403D-15: A compact diesel with comparable output, requiring custom mounts.
  
• Honda GX690 (gasoline): Occasionally used in retrofit builds, though torque and hydraulic compatibility may suffer.
  

Before selecting an engine, verify:

• Bellhousing bolt pattern and shaft alignment.
  
• Flywheel diameter and coupler compatibility.
  
• Exhaust clearance and air intake routing.
  
• Electrical harness and throttle linkage integration.
  

Some owners fabricate adapter plates or modify engine mounts to accommodate newer engines. In one retrofit, a technician used a plasma cutter to reshape the mounting plate and installed rubber isolators to reduce vibration.
Removal and Installation Process
To remove the old engine:

• Disconnect battery and drain fluids.
  
• Remove rear access panel and lift arms for clearance.
  
• Disconnect fuel lines, throttle cable, and wiring harness.
  
• Unbolt engine mounts and lift engine using a hoist.
  

During installation:

• Align flywheel coupler precisely—misalignment causes pump damage.
  
• Torque mounts to spec and use thread locker.
  
• Reconnect all lines and test throttle response.
  
• Prime fuel system and check for leaks.
  

Use a laser alignment tool if available to ensure coupler concentricity. Improper alignment can lead to premature pump wear or shaft failure.
Recommendations and Field Tips

• Always measure engine dimensions before purchase—some newer engines are taller or wider.
  
• Retain the original radiator and fan shroud if possible to avoid cooling issues.
  
• Use high-quality motor mounts to reduce vibration and noise.
  
• Install a temperature gauge and oil pressure sensor for early warning.
  

Document all modifications for future service. If selling the machine, disclose the engine swap and provide part numbers for replacement components.
Closing Reflections
Swapping the engine on a Bobcat 751 is a mechanical challenge that blends fabrication, hydraulics, and patience. When done correctly, it breathes new life into a machine that still has years of work ahead. Whether clearing snow, grading gravel, or feeding livestock, a well-executed engine swap transforms the 751 from a tired relic into a reliable partner—ready to roll, lift, and dig once again.