Every boat insurance policy has exclusions. The excluded items vary from company to company but typically include loss caused by gradual deterioration, mold, insects, animals and marine life, wear and tear, and weathering. Some companies include coverage for damage caused by zebra mussels; others do not. Other excluded items may include: scratching osmosis, blistering, corrosion, except electrolytic (stray current) corrosion, denting, marring, manufacturer’s defects, or defect in design.
Typically policies also exclude items having a latent defect that causes damage to your insured property; however, resulting damage may be covered. If your water pump is defective, a policy may not pay for the water pump but may pay all resulting damage to the engine.
Some boat insurance policies have machinery damage exclusions and others do not. Forget to put oil in your engine and the policy that does not have a machinery damage exclusion may provide coverage; the policy with the machinery damage exclusion would most likely not cover the loss.