USCG Tests Using Diesel Outboards On Fast Rescue Boats

Diesel Outboard Engines
USCG Response Boat-Small test platform outfitted with Mercury Marine 175HP
spark-ignited diesel outboard engines. U.S. Coast Guard photo.

Gasoline is the dominant fuel source for Fast Rescue Boats aboard merchant ships but it is difficult to obtain, dangerous to store and has a limited shelf life aboard ship. Diesel fuel has none of those problems. Can it be a suitable replacement? 

The United States Coast Guard has been researching this topic. Here is their report:

by Loretta Haring
Office of Strategic Planning and Communication Acquisition Directorate, USCG

Is it possible for the Coast Guard to power its surface fleet using only one type of fuel? The Coast Guard Research and Development Center is investigating using diesel outboard engines.

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The Coast Guard currently uses both diesel and gasoline to fuel its surface fleet; while diesel is the dominant fuel for cutters and many boats, the service operates hundreds of gasoline-powered outboard engine boats. Conversion to a single-fuel fleet could improve safety and reduce costs.

“Having a single-fueled fleet could benefit the entire Coast Guard cutter and boat fleet with fuel sources, fuel contracts, fuel logistics, fuel storage, maintenance, training and overall support,” said Lt. Cmdr. Hector Maldonado, a sponsor representative with the Coast Guard Office of Naval Engineering.

The RDC, based in New London, Connecticut, is in the third phase of the project – actual testing of diesel outboard engine technology. Testing covers performance assessments as well as long-term reliability, availability and maintenance data collection. Three engines – Mercury Marine’s 175HP spark-ignited diesel engine and the OXE 200HP and Cox Powertrain 300HP compression-ignited diesel engines – will be tested through Cooperative Research and Development Agreements, CRADA, with industry.

“Since this technology is so new, industry partners are just as eager as the Coast Guard to put real operational hours on these engines to better understand their capabilities and limitations,” said Lt. Keely Higbie, a member of the RDC’s Diesel Outboard Engine team. “Under the CRADA, we are integrating industry’s technology onto active Coast Guard platforms and providing the man-hours necessary to collect this information for both parties.”

The RDC is wrapping up the testing on Mercury Marine’s 175HP engine at Coast Guard Training Center Yorktown in Yorktown, Virginia.

“Training Center Yorktown has provided technical and operational expertise and support to date, working with both the RDC and industry to effectively integrate these engines onto their boat platforms,” said Lt. Carl Brietzke, the RDC’s Diesel Outboard Engine project manager. “These engines are getting a lot of exposure at the training center, which is fueling excitement within the Coast Guard about what future boat fleets might look like.”

Testing on the compression-ignited diesel engines will begin at Yorktown in the first quarter of fiscal year 2018.

Diesel Powered USCG Response Boat
Launching the Response Boat -Small for performance testing of the 175HP
Mercury Optimax diesel outboard engines. U.S. Coast Guard photo.

To initiate the project, the RDC conducted a market survey to find the characteristics and development status of diesel outboard engines in the 150 to 300HP range now available on the market. Data from the survey was used to develop a cost-benefit analysis. The operation, performance and maintenance cost part of the study focused on the response boat-small platforms, which make up 40 percent of the Coast Guard’s outboard engine fleet.

Ultimately, the analysis concluded that the Coast Guard can experience significant operation, maintenance, infrastructure and logistics cost savings through integrating diesel outboard engine technology into future boat fleet designs.

Benefits of a single-fuel fleet
• Improved interoperability with Coast Guard cutters, Department of Defense assets, and foreign nations due to increased fuel availability
• Reduced concerns about fuel availability during natural disasters or other major events
• Elimination of half of the Coast Guard’s fueling infrastructure
• Improved fuel storage stability concerns
• Opportunities for drop-in replacement with renewable fuel

The results of the cost-benefit analysis were shared at the Multi-Agency Craft Conference in June 2016. As a result, the Army Corps of Engineers and U.S. Navy have engaged the RDC to leverage the work done to conduct similar analyses to possibly prove a transition to diesel for their fleets as well.

“This project is a great example of government agencies working together to end duplication of efforts,” said Lt. Steven Hager, Research, Development, Test and Evaluation (CG-926) domain lead for the project. “There are clear benefits to all agencies operating outboard powered boat fleets, and sharing knowledge and processes used to date helps advance this effort toward implementation and a better product to the American people.”