The tangible negative sides of small vessels with outboard outboard motors include high fuel consumption in relation to the generated power, as well as their low environmental characteristics, expressed in harmful emissions, harmful discharges. When assessing the impact of the impact of the entire world fleet on the environment, small-sized small vessels should not be neglected because of their massive prevalence. Experimental data aimed at improving the environmental characteristics of an outboard outboard motor by reducing harmful emissions by injecting water in the fine-dispersion phase into the suction manifold of the engine are considered. The environmental characteristics of water supply to the intake manifold of a four-stroke outboard outboard motor are analyzed; regulatory and technical doc-umentation concerning the limitation of harmful emissions on small vessels with outboard outboard motors is investi-gated; the existing methods of water supply to the intake manifold of four-stroke engines are considered and a patent search is conducted. A device generating a fine-dispersed fog-like cloud was installed on the outboard motor engine, an experimental assessment of the content of harmful emissions in exhaust gases was carried out in terms of components such as carbon monoxide, carbon monoxide and nitrogen oxides when water is supplied to the intake manifold of a four-stroke outboard motor by laboratory measurements in a small experimental pool and outdoors. The content of harmful emissions in exhaust gases is estimated when water is supplied to the intake manifold of a four-stroke outboard motor. The ecological effect of installing a water supply device into the intake manifold of a four-stroke outboard outboard motor is analyzed. A four-stroke outboard outboard motor with a capacity of 4 hp and a change in its environmental characteristics when water is injected into the cylinder are investigated.