Abstract: This presentation reviews the findings of a Cost Benefit Analysis (CBA) conducted by the U. S. Coast Guard Research and Development Center on the potential implementation of diesel outboards on Coast Guard boats. Currently, the Coast Guard is operating a two-fuel surface fleet: diesel and gasoline. Diesel dominates as cutter fuel and fuel for many inboard propulsion systems. The Coast Guard also operates hundreds of gasoline-powered outboard engine boats which results in duplicative infrastructure at shore units, creates interoperability issues with Department of Defense and foreign nations, and poses increased safety risks during fuel handling. This CBA evaluated the costs associated with moving towards a single-fuel surface fleet by converting these gasoline powered outboard engine boats to diesel and also examines the benefits and risks associated with the implementation. It considers implementing diesel outboard engines in the near-term future (next 1-2 years) by retro-fitting them onto the existing boat fleet as well as the long-term future (next 5-10 years) which includes diesel outboard engines as part of the design of the next generation boat fleet. Due to the expansive and diverse nature of the Coast Guard’s boat fleet, this analysis was simplified to focus on the largest group, the Response Boat – Small (RB-S) which uses 40% of the Coast Guard’s outboard engines, for data on the procurement, installation, operation, maintenance, and disposal cost analyses. Additionally, the CBA attempted to quantify what the affects would be on the logistics and infrastructure of the Coast Guard if only a single fuel was required to conduct operations. The CBA showed that for most Coast Guard boat types it is not cost effective to convert existing boats to diesel in the near-term future because the high cost of procurement, system installation, and integration associated with retro-fitting are not offset by the performance benefits and maintenance cost savings. However, some Coast Guard boat types with the highest annual operating hours could realize a near term cost savings. The CBA also determined that in the long-term the procurement costs of diesel outboards will decrease as the technology matures and diesel outboards can be designed into future boat fleets, eliminating retro-fitting costs and making them the preferred outboard propulsion system.