Replacing a KTA19 with a Mitsubishi S6A3-Y1/Y3 and S6R-Y1/Y3 

Replacing a Cummins KTA 19 with a Mitsubishi S6A3 and S6R

Repowering a vessel from a Cummins KTA19 to a Mitsubishi S6A3 or S6R requires evaluating piping layout, mounting geometry, gear compatibility, and cooling capacity. The S6A3 is closer to the KTA19 in size and typically installs with fewer modifications, while the S6R delivers higher horsepower but introduces added demands in cooling, exhaust flow, and air intake. Many operators are moving away from the KTA19 platform due to long lead times and uncertainty tied to rebuilt engines, making Mitsubishi’s mechanical reliability and consistent parts availability an appealing long-term solution.

Jump to:

• Power & Configuration Differences
• Common Modifications to Plan For
• Third Party Stories & Field Notes
• Target Market
• Repower Planning Summary

Power & Configuration Differences

• Piping rerouting may be required under the engine or toward the front or sides.

• New or modified mounting pads will be necessary to match Mitsubishi mounting patterns.

• Cooling system updates are expected, especially for the S6R, including coolant routing changes and added cooling capacity.

• New mufflers will be required for the S6R to handle increased exhaust flow.

• Additional or enlarged air intakes will be needed, particularly for the S6R Tier 3 installation.

Third-Party Stories & Field Notes (As of February 2022)

• Boone Towing: Their newest vessel went straight into dry dock to replace its engines with Mitsubishi. The company is so satisfied with Mitsubishi performance and reliability that their entire fleet now runs Mitsubishi engines.

• Jantran: Their vessel, the Mr. Tom, recently dropped a KTA19 and learned a replacement engine would take 10 months. After repeated long lead-time issues, they chose to switch to Mitsubishi. The boat is now being surveyed for installation of S6R-1800s.

• Cummins Recon Program Realities:

  • Cummins offers rebuilt engines at two-thirds to three-quarters the cost of a new engine and includes a two-year warranty, which sounds appealing upfront.

  • The drawback is no visibility into engine history — operators don’t know how many hours or rebuild cycles a recon engine has seen.

  • Failures can occur within months due to metal fatigue on older internal components, forcing operators back into dry dock and erasing any cost advantage.

  • These risks are pushing more operators to prefer new, mechanically simple Mitsubishi engines with predictable lifecycle performance.

Target Markets

These engines are widespread across multiple sectors, and ongoing issues with parts availability, long lead times, and declining reliability make Mitsubishi a strong alternative. If the vessel floats, it is essentially a target market.

Key segments include:

• Inland river push boats operating high annual hours and needing dependable mechanical power.

• Harbor and coastal tug boats looking for stronger durability and easier long-term maintenance.

• Offshore tugs and supply vessels where uptime and service access are critical.

• Ferries and workboats that benefit from consistent torque delivery and reduced electronic failure points.

IRR Companies with KTA 19 Boats (As of February 2022)

Repower Planning Summary

Primary Required Changes

General Observations

• The S6A3 typically requires fewer modifications and fits more easily into KTA19 footprints, while the S6R introduces higher cooling and airflow demands.

• Operators shifting from KTA19s are motivated largely by reliability, lead-time issues, and the long-term advantages of mechanical engines.

• Vessel-specific constraints — especially piping paths, mounting geometry, and available cooling capacity — drive which Mitsubishi model is the best fit.