A clean, well-operating boat lasts longer and reduces the amount of pollutants entering the water. Tune your engine regularly. In turn, your engine will operate more cleanly, will have increased fuel efficiency, and will last longer. Steam clean your engine in a dedicated service area, rather than using harmful engine cleaners. Inspect your fuel lines.
Unleaded fuels can contain alcohol, which corrodes rubber hoses.
Use non-toxic bilge cleaners. Many bilge cleaners are harmful to the water environment because they merely break down oil into microscopic fragments which are pumped out in the bilge water. Most non-toxic bilge cleaners digest hydrocarbons rather than emulsifying them. Marine dealers should have more information. Dispose of all maintenance products and chemicals properly.