Boston Whaler 20 Justice Series, Operation & Maintenance Manual

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6-7
Boat Maintenance Section 6
Hull Blistering
The chemical and physical structure of all fiberglass
boats is somewhat porous. Water can permeate
through gelcoat and fiberglass during long periods of
immersion in water. This process is referred to as
hydrolysis .
The effect of hydrolysis over time allows water to enter
the gelcoat and substrate, forming a blister. Blistering
is caused by the deterioration of certain water-soluble
materials in the hull laminate. Blisters can form in
near-surface layers of gelcoat or very deep in the
fiberglass substrate.
The damage can range from cosmetic to structural,
although structural damage is a rare occurrence.
Studies point to long-term immersion of a boat in warm
water as a primary cause of hull blisters. Stress
cracks on the hull below the waterline can also contrib-
ute to the formation of blisters.