Galvanic stack on a leaking pedestal.

§1Facts of the loss

The Cobalt 333 had been moored at slip B-14 since June 2024 on a seasonal lease with the marina. The boat used the slip’s 30 A 125 V shore-power pedestal continuously for refrigeration, battery charging, and bilge-pump backup. The owner — a retired Mercyhurst Prep teacher whose name appears in the sealed file — had observed no unusual electrical symptoms in the preceding three months. The boat’s electrical inspection (May 2024, prior to splash) had been performed by an ABYC-certified marine electrician and had passed without notation.

The afternoon of 14 September was overcast and humid; the marina’s electrical loads were close to normal for late season. The owner left the boat at 18:30 EDT after dinner ashore and did not return until the bilge alarm summoned him at 04:18. By that time the bronze through-hulls on the starboard side were unrecognizable — the raw-water intake had eroded from a 1-inch nominal fitting to approximately 3/8 inch internal diameter, and the seacock was no longer functional. The starboard prop shaft showed visible pitting along its full length; the rudder post had wasted by perhaps 30% of original cross-section.

The local Coast Guard Auxiliary attended the scene at 05:50 EDT and authorized the emergency tow at 07:42. The boat was hauled at the Presque Isle State Park public ramp and surveyed dry by a marine surveyor at the owner’s insurer’s request later that day. Total claim — $184,500, comprising vessel repair (drive-train, rudder, through-hulls, electrical-system audit), tow, and storage.

§2The pedestal

The Cobalt’s shore-power supply was at slip B-14’s pedestal — a circa-2008 weatherproof unit with a 30 A 125 V receptacle. The pedestal’s service was fed from the marina’s 240/120 V single-phase distribution panel via a 250-ft direct-burial run in PVC conduit beneath the gravel walkway between the panel and the slip. The cable installation appeared original to the 2008 construction.

The pedestal’s equipment-grounding conductor — the green-wire bond between the receptacle’s ground terminal and the marina’s shore-side grounding system — was the failure point. Field examination of the pedestal on 16 September (two days after the loss) showed: the EGC terminal at the receptacle’s back was clean and intact; the green wire entering the pedestal from below was visibly bright (recent disturbance); below grade, however, the EGC had been spliced in the underground portion of the conduit run during a 2018 trenching incident when the marina’s walkway irrigation line was replaced. The splice had been made with a single Polaris-style insulated splice block, buried in the original location, and subjected for six years to seasonal freeze-thaw cycles and salt-spray penetration from the Lake Erie shore.

By 14 September 2024 the splice had become a high-impedance connection — the firm measured 4.7 Ω resistance from the pedestal’s ground terminal to the marina’s service-entrance grounding electrode system, against an expected reading of well under 0.5 Ω. The high resistance was sufficient to interrupt the boat’s reference to shore-side ground; the boat’s onboard bonding system (which connects the boat’s engine block, all underwater fittings, and the boat’s sacrificial zinc anode through-the-hull) then floated relative to other boats on the same marina dock.

§3Galvanic mechanism

The mechanism the matter rests on is straightforward marine electrical galvanic corrosion. Two boats moored on the same marina dock, both supplied from the same shore-side grounding electrode system, normally share a common reference; their underwater metal fittings sit at the same potential relative to the water and no current flows between them. When one boat’s shore-side ground reference floats — as the Cobalt’s did when the pedestal-side EGC splice degraded — that boat’s underwater fittings can sit at a meaningfully different potential than the neighboring boats’.

The neighboring slip B-13 was occupied that night by a 27-foot Sea Ray with intact ground reference and an oversized stainless-steel skeg. The potential difference between the Cobalt’s bronze through-hulls and the Sea Ray’s stainless skeg drove a galvanic current through the 80-foot water column between the two boats. The current consumed the bronze (the less-noble metal in the galvanic couple); the stainless skeg was unaffected, and the Sea Ray’s owner is to this day unaware of the role his boat played in the matter.

The rate of consumption — bronze through-hulls reduced to a fraction of original cross-section in approximately twelve hours — implies a galvanic current of order 80 to 120 mA. This is consistent with what ABYC E-11 §11.5.2 calls a “catastrophic galvanic event” — distinguishable from normal slow galvanic action (which an intact sacrificial anode mitigates) by the rate of consumption and by the involvement of multiple non-anode fittings simultaneously.

§4Finding

The loss to the Cobalt 333 at slip B-14 of the Presque Isle State Park marina on the night of 14–15 September 2024 was caused by catastrophic galvanic action on the vessel’s underwater bronze fittings, driven by a potential difference between the vessel’s onboard bonding system and the shore-side grounding electrode system of the marina. The potential difference resulted from a high-impedance underground splice in the equipment-grounding conductor between the marina’s service-entrance grounding electrode system and pedestal B-14, installed in 2018 by an irrigation contractor working under no electrical-installation authorization and buried without inspection. The marina’s grounding-system audit obligations under ABYC E-11 §11.4 (annual continuity test) had not been performed since 2017. Sealed PE report · 28 February 2025 · Trzaska / Marcantonio

The finding supported subrogation pursuit by the boat owner’s insurer against both the marina (failure to maintain grounding system) and the 2018 irrigation contractor (unauthorized electrical work). Settlement was reached in May 2025 with the marina’s commercial liability carrier; the contractor settled separately for an undisclosed sum the following month.

§5Aftermath

The Presque Isle State Park marina, on receipt of the firm’s sealed report in March 2025, retained Presque Isle PFE for a complete grounding-system audit of all 116 pedestals at the marina’s four docks. The audit (filed under CF-2025-022) found three additional high-impedance EGC connections and twelve pedestals with bonding-jumper degradation traceable to similar trenching incidents over the marina’s twenty-year operating history. The marina’s annual grounding inspection has since been brought up to the ABYC E-11 §11.4 standard and is now performed by a different ABYC-credentialed contractor.

The matter is the firm’s most-cited marine-electrical example. Doménico Marcantonio’s contribution to this Case File — he conducted the pedestal-by-pedestal field survey under Dr. Trzaska’s direction and authored the survey workbook that became Exhibit C-014 — was the first independent EIT work he had performed for the firm; the audit became part of his pre-PE experience documentation submitted to the Pennsylvania State Board for PEs in October 2025.

§6References