Jet Ski Modifications and Insurance: What You Must Declare

Many jet ski owners modify their craft after purchase — adding aftermarket exhausts, performance engine tunes, upgraded impellers, custom graphics, or fishing electronics. These additions improve the ownership experience, but they also have implications for insurance that are often overlooked until a claim arises. Understanding what you need to declare and when is essential to maintaining valid cover.

The starting principle is disclosure. Insurance policies are contracts of utmost good faith, which means the policyholder is required to disclose all material facts relevant to the risk being insured. A material fact is anything that would influence a reasonable insurer's decision to offer cover and on what terms. Modifications that affect performance, value, or risk profile are almost always material facts, and failure to disclose them — even unintentionally — can affect the insurer's ability to pay a claim.

Performance modifications are the most significant category from an underwriting perspective. An engine tune, ECU remap, or aftermarket exhaust that increases output beyond the manufacturer's specification changes the risk profile of the craft in ways that insurers care about. Higher-performance craft accelerate faster, reach higher speeds, and place different stresses on structural components. Underwriters price for the standard specification of a craft; a materially more powerful version of that craft may attract different terms or premium. Declaring performance modifications at application or renewal is essential.

Value-affecting modifications must be declared to ensure the sum insured remains accurate. Factory specification forms the baseline for any market value assessment, and a craft with significant aftermarket additions — a Garmin chartplotter, high-end audio, carbon fibre trim, or custom seating — has a total value above the standard model. If those additions are not noted in the policy, they may not be covered in a total loss settlement, and you may receive a payout that does not reflect the full cost of what was lost.

Non-standard fittings that are permanently attached to the craft — rod holders, anchor systems, trolling motor mounts, storage modifications for fishing use — should be listed as part of the craft's specification rather than treated as accessories. The distinction between what is part of the craft and what is a removable accessory affects how both are covered under the policy.

If you acquire a second-hand craft that already has modifications in place when you buy it, you are responsible for disclosing those modifications when applying for cover. The fact that you did not make the modifications yourself does not remove the obligation to declare them.

Timing matters. Modifications should be declared at inception when first purchasing a policy, or at the point when they are made to a craft already under an existing policy. Waiting until renewal to declare a modification that was made mid-year creates a gap — if an incident occurs before that declaration is made, cover may be affected. Contacting your broker or insurer promptly when a modification is made is the safest approach.

Not all modifications increase risk or premium. Security improvements — GPS trackers, immobilisers, quality hitch locks — are modifications that typically attract positive underwriter recognition rather than additional loading. Cosmetic changes that do not affect performance or significantly affect value are generally low risk from a disclosure perspective, though when in doubt, declaring is always the safer choice.

A specialist marine broker is the best resource for understanding how specific modifications on your craft should be declared and whether they are likely to affect your premium. Having a clear conversation before modifying your craft — rather than after — means you can make informed decisions about what you want to do and what the insurance implications will be.