While comfortable and aesthetically pleasing, leather boat seats are also prone to mould and algae development. However, with a little elbow grease and a few simple cleaners you can have your leather seats looking like new.
Brush off the boat seats with the stiff brush. This will remove the majority of mould and mildew from the seats.
Wipe the seats with a clean, wet towel. This will remove stubborn areas of mould and algae. Continue cleaning, using a new towel when needed, until seats appear clean.
Use the old toothbrush to clean difficult areas, such as seams and creases.
Apply leather cleaner to the seats to deep-clean and condition the seats.
Allow boat seats to dry in the sun.
A solution of equal parts alcohol and water can be used in lieu of commercial leather cleaner and will provide equal results. Avoid leaving your boat seats wet to prevent mould and algae build-up.