How do i paint the bottom of my boat?

Question

what are the masurements for thinning the paint? are there any steps i need to take to prep it, and what should i sand it with if it's already painted?

Answer 1

A gallon usually covers about 400 square ft.  No need to thin, use paint as is.  Buy a good anti-fouling paint  that is designed to  be applied directly over existing paint.  Follow directions on paint can for surface preparation.  At minimum, sand entire bottom with 100 grit sand paper.  Be sure to mask waterline and also, a half inch around out-drive if boat has one.  DO NOT let paint touch out-drive as this will accelerate corrosion of the drive unit.  Paint can be applied with roller or brush.

Answer 2

Bottom paints contain some nasty chemicals.  Many cannot be sold to nor applied by consumers.  You need proper safety equipment to consider doing this job yourself.  Cleaning/sanding the old paint is extremely hazardous without the proper breathing protection.  Application by brush or roller of the new paint is not as hazardous.  Spray application is dangerous.

You need to know the chemicals/hazards of both the old paint and new paint and understand what safety equipment is required as well as disposal requirements.

Bottom line, not recommended for the inexperienced.