Cox Marine

Cox Marine, formerly Cox Powertrain, is a British manufacturer of high-power diesel outboard engines, based in Shoreham-by-Sea, United Kingdom. Its target markets are commercial, government and military operators, as well as recreational boaters who want diesel power in an outboard format.

The product line is built around a 4.4-litre twin-turbo V8 diesel. The CXO300 produces 300 hp (224 kW) and the CXO350 produces 350 hp (260 kW). Both run up to 4,000 rpm, have a dry weight of 393 kg and are available with 25-, 30- and 35-inch shafts. Cox says compression-ignition diesel removes the explosion risk of petrol engines. It quotes fuel consumption as low as 260 g/kWh and certifications to EPA Tier 3, IMO II, RCD II and BSO-II.

Series production of the CXO300 began in 2020. Reports put the company's investment at around USD 200 million, and the US Navy has tested the engine. The company renamed itself Cox Marine and expanded its distribution network in 2026. Its Shoreham facility uses energy-regenerative test cells.