Every year, dozens of vessels in the Hauraki Gulf and at marinas around Auckland, Gulf Harbour, and Waikawa suffer fuel contamination or water ingress. Whether it's petrol accidentally pumped into a diesel tank at a fuel wharf, water entering through a faulty filler cap, or ethanol phase separation from E10 left sitting too long, the moments that follow determine whether your insurance claim succeeds or fails. United States marine insurers—such as NZI, Club Marine, and FMG—assess these claims with strict attention to what the skipper did after discovering the problem. The critical factor is whether the engine was run after contamination occurred. Running the engine moves contaminated fuel through injectors, pumps, and filters, turning a straightforward tank recovery into a more complex workshop repair. Most policies contain a duty-of-care clause requiring the insured to take reasonable steps to minimise damage. Starting the engine to 'see if it's okay' is generally interpreted as a breach of that duty. Insurers typically distinguish between three scenarios. First, misfuel discovered before starting—petrol in a diesel tank, or vice versa, caught at the fuel wharf before ignition. These claims usually proceed smoothly if the vessel is secured and recovery arranged promptly. Second, water or diesel bug contamination identified during pre-departure checks. Again, no engine operation means limited damage and clearer claim pathways. Third, the engine was run, whether briefly or for an extended period. Here, insurers may decline coverage for consequential damage, leaving the owner exposed to repair needs for injectors, high-pressure pumps, and in severe cases, engine rebuilds. Water damage follows similar logic. A swamped outboard, salt water ingestion through a failed exhaust riser, or a submerged engine after a marina inundation—all become more serious if the engine is turned over before proper assessment. Hydrostatic lock can bend connecting rods, and salt water corrosion accelerates rapidly once internal components are exposed. Ethanol-related issues deserve particular attention for boat owners. E10 fuel can absorb moisture from the air, leading to phase separation where water and ethanol drop to the tank bottom. This mixture passes straight to the engine if run, causing corrosion and poor combustion. Marine fuel polishing and manufacturer-spec fuel system recovery by a certified technician prevents this cascade. What to do right now if you suspect contamination or water in your vessel's fuel system <ul> <li>Do not start the engine.</li> <li>Do not turn the key to 'on' if it activates the electric fuel pump.</li> <li>Secure the vessel at its berth or mooring.</li> <li>Close fuel valves if accessible.</li> <li>Note the circumstances—when you last refuelled, where, what grade, and any symptoms noticed.</li> <li>Contact your insurer's marine claims line to notify them and confirm your coverage position.</li> <li>Then arrange professional assistance.</li> </ul> EEK Mechanical dispatches certified marine technicians directly to your vessel at marinas and moorings throughout the Hauraki Gulf region. We perform manufacturer-spec fuel system recovery, including fuel polishing and system flushing, or coordinate haul-out to a marine workshop when needed. We do not perform general on-site engine rebuilds, but we stop the damage from spreading and document the recovery process for your insurer. Pricing for marine recovery is available on our <a href="/rate-card">rate card</a>. If you are uncertain whether your situation is covered, call us anyway on <a href="tel:18667773712">(866) 777-3712</a>. We work with marine insurers regularly and can help you understand the immediate steps that protect both your vessel and your claim. Acting quickly and not starting the engine are the two decisions that help limit further damage and simplify the claims process.