Nylon tarps trap moisture against your boat's hull and deck instead of letting it escape, creating a humid environment that accelerates mold, mildew, and gelcoat deterioration over any storage season longer than a few days.
Nylon is not breathable — air and water vapor cannot pass through the weave, so condensation builds up underneath whenever temperatures fluctuate. That trapped moisture softens upholstery, corrodes metal fittings, and feeds mold colonies that can take hold in as little as 48 hours in humid climates. Nylon also degrades quickly under UV exposure, turning brittle and cracking within a single outdoor season, which leaves your boat exposed at exactly the wrong moment. A purpose-built marine cover uses a coated Oxford fabric construction with integrated vents precisely to avoid both failure modes.
- Nylon tarps offer no breathability rating — trapped vapor raises under-cover humidity significantly compared to vented marine covers.
- Mold colonies can establish on boat upholstery in as little as 48 hours in humid conditions above 60% relative humidity.
- Nylon degrades under UV without a rated anti-UV coating, typically cracking or tearing within one outdoor storage season.
- Marine-grade 1200D Oxford covers are rated to 9600pa water resistance versus the near-zero waterproof rating of standard nylon tarps.
- Solim pontoon covers include dual rear air vents specifically to allow moisture to escape — a design feature absent on nylon tarps.