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Replacing a CAT C32 1000HP @1800 with a Mitsubishi S12R-Y3 1100 HP @ 1800 RPM

Understand the physical, performance, and cooling requirements when replacing a CAT C32 1000 HP @ 1800 RPM engine with a Mitsubishi S12R-Y3 1100 HP @ 1800 RPM.

Replacing a CAT C32 with a Mitsubishi S12R

This comparison outlines the key differences between the CAT C32 and the Mitsubishi S12R-Y3 rated at 1100 HP at 1800 RPM. It focuses on physical size, performance, fuel consumption, and the real-world modifications required for a repower. While the S12R is a larger, higher-displacement engine, this overview highlights how it compares at equivalent operating power, where fuel burn, reliability, and long-term operating costs matter most. The goal is to provide a clear, upfront view of what a C32-to-S12R repower involves so operators can make an informed decision without surprises later in the project.

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Power & Configuration Difference

Metric CAT C32 Mitsubishi S12R-Y3
HP Rating 1000 HP @ 1800 RPM 1100 HP @ 1800 RPM
Configuration V-12 V-12
Displacement  32.1 L 49.4 L (52% more)
Weight

7100 lbs

 11729 lbs
Bell Housing Single 0 Double 00
HP/Liter 31.15 22.44
LBS./HP 7.1 10.66

Dimensional Delta: CAT C32 vs Mitsubishi S12R-Y3

Dimension CAT C32 Mitsubishi S12R Delta
Length 70.0 in 94.13 in  +24.13 in
Width 60.2 in 59.54 in -.66 in
Height 62.5 in 68.78 in +6.28 in

 Why this matters:

  • Length: The S12R is approximately 20 inches longer than the C32, making length the most significant dimensional difference to plan for in a repower.

  • Width: Engine width is very similar between the S12R and the C32, with no meaningful clearance advantage either way.

  • Height: The base S12R engine is only slightly taller than the C32, with most added height coming from the bell housing, flex, and mounting components.

Performance Characteristics

Metric CAT C32 Mitsubishi S12R-Y3
Exhaust Flow (CFM)

5099

 8368
Exhaust Size (Typical)

10

 12
Intake Air Flow (CFM)

2423

 3178
Intake Pipe Size (Typical)

6

 8
Jacket Water Heat Rejection

26388 BTU/min

 23800 BTU/min
Jacket Water Flow Rate (GPM)

201

 454
Heat Rejection to After Cooler 8609 28,825
After Cooler Flow Rate (GPM) 106 53
Fuel Consumption @ 1000 HP 49.2 49.2

Key Notes

    • The CAT C32 is a 32-liter engine, while the Mitsubishi S12R is a 49-liter engine, putting them in completely different displacement classes.

    • The S12R has approximately 52% more displacement than the C32, which is immediately understood by most operators.

    • Both engines operate at 1800 RPM, allowing for a direct comparison at operating speed.

    • The S12R-Y3 is rated at 1100 horsepower, providing about 100 more horsepower than the typical C32 application.

    • Horsepower per liter is lower on the S12R, at roughly 22 HP/L compared to 31 HP/L on the C32, indicating a less stressed engine design.

    • Exhaust flow is significantly higher on the S12R due to increased displacement.

    • At full rated power, the S12R burns more fuel, but this is not the most relevant comparison.

    • When evaluated at equivalent operating power around 1000 horsepower, fuel consumption between the two engines is comparable.

    • Matching fuel burn at equal power is notable given the S12R’s larger size and mechanical design.

    • Fuel cost represents the majority of annual operating expense, making apples-to-apples fuel comparison a major decision factor.

    • The S12R offers comparable fuel consumption while providing long-term reliability, support, and service life advantages.



    Common Modifications to Plan For

    Cooling System

    • The S12R requires a dedicated aftercooler, which is significantly larger than what is typically installed with a C32.

    • Existing jacket water coolers may be reusable, but flow rates and capacity must be confirmed on a vessel-by-vessel basis.

    • In many cases, a larger or modified cooler box will be required to accommodate the S12R aftercooler.

    • Double-stacking coolers may be possible, but overall cooling package size will still be substantially larger than the C32 setup.

    Exhaust System

    • The S12R produces higher exhaust flow and requires larger exhaust components.

    • Typical C32 installations use 10-inch exhaust piping, while the S12R will require 12-inch exhaust piping, with some muffler configurations requiring up to 14 inches.

    • Existing mufflers and exhaust piping are not expected to be reusable.

    Air Intake System

    • Increased air demand on the S12R requires larger intake piping and filtration compared to the C32.

    • Intake system sizing must be reviewed as part of the repower survey.

    Engine Mounting & Structure

    • The S12R is substantially heavier than the C32 and will require new mounting pedestals.

    • Engine foundations must be reviewed to ensure adequate structural support for the added weight.

    Bell Housing & Drivetrain Interface

    • A bell housing adapter will be required to mate the S12R to the existing gear.

    • This adapter is already a known and manageable component of the repower.

    Engine Room Clearance & Access

    • Additional engine length requires clear access space forward of the engine for service and safe personnel movement.

    • Obstructions in front of the engine may need to be relocated or modified.

    Survey & Yard Considerations

    • This is not a drop-in replacement, and shipyard work should be expected.

    • Modifications should be identified early to avoid late-stage surprises during installation.

    • Some vessels may require updated inspections or COI review, particularly if cooling systems or hull penetrations are modified.

    Third Party Feedback & Market Observations 

    • Operators and fleet owners have reported growing frustration with the CAT C32 platform, particularly around durability and long-term reliability.

    • Feedback from the field indicates recurring issues with injectors, cylinder heads, blocks, shafts, bearings, and journals as engines age.

    • Many C32 installations begin showing significant problems in the four-to-seven-year operating range, leading owners to avoid installing additional C32s in their fleets.

    • Despite some public claims of satisfaction, industry feedback suggests a majority of operators are dissatisfied with long-term performance.

    • New CAT C32 availability has been reported at extended lead times, with operators waiting many months for replacement engines.

    • Reported pricing for new C32 engines has ranged from approximately $230,000 to $250,000, increasing frustration when paired with downtime.

    • Many existing C32s in the market are relatively young, creating a near-term repower opportunity as dissatisfaction continues to build.

    • Conversations with operators suggest this repower opportunity is expected to expand significantly over the next one to three years.

    • Extended vessel downtime while waiting on replacement C32 engines is a major operational and financial concern for operators.

    Repower Planning Summary

    Primary Required Changes

    • Larger aftercooler and associated cooling components

    • New engine mounting pedestals

    • Bell housing adapter

    • Larger mufflers and exhaust piping

    • Larger air filters and intake piping

    • Verification of adequate front and overhead engine room clearance


    General Observations

    • The S12R is a significantly larger, higher-displacement engine than the C32, placing it in a different engine class rather than a like-for-like replacement.

    • This repower is not a drop-in swap and requires upfront planning, shipyard work, and clear communication to avoid late-stage surprises.

    • When evaluated at equivalent operating power, fuel consumption is comparable despite the S12R’s larger size and mechanical design.

    • Market frustration with the C32, combined with long lead times and high replacement costs, creates a growing repower opportunity over the next one to three years.