The Marine-Puck MP3.6 is a compact 3.6 kVA toroidal marine isolation transformer designed for safe, reliable shore power on boats and smaller yachts. It features a hermetically epoxy-encapsulated toroidal transformer inside a rugged, flame-rated non-metallic ABS plastic enclosure. This Class II double-insulated construction provides complete galvanic isolation with no ground reference to the enclosure or boat ground.
Because the enclosure is non-metallic, it cannot be grounded and delivers superior corrosion resistance compared to most stainless-steel alloys in harsh marine environments. The solid epoxy potting compound locks all internal connections in place, eliminating vibration-induced loosening, shorts, or arcing while preventing seawater ingress. The result is a lightweight, compact, and virtually maintenance-free isolation transformer that protects vessels from galvanic corrosion, stray currents, and electrical hazards far more effectively than traditional designs.
Key Benefits
- Stops nuisance GFI tripping on shore power
- Eliminates galvanic corrosion of metal hulls, shafts, and propellers
- Provides true Class II double insulation (no ground reference)
- Hermetically sealed epoxy potting prevents seawater ingress
- Non-metallic ABS enclosure offers superior corrosion resistance
- Quiet toroidal design – no annoying hum
- Significantly lighter and smaller than conventional laminated transformers
- Soft-start included
- 104 V and 208 V boost included
- UL Listed Marine (E509703) and Ignition Protected
Technical Specifications
| Specification | MP3.6-30A |
|---|---|
| Continuous Power | 3.6 kVA |
| Frequency | 50/60 Hz (International) |
| Input Voltage | 120/240 V |
| Output Voltage | 120/240 V |
| Dimensions | OD 10″ × Height 5″ |
| Weight | 50 lb |
| Enclosure | Flame-rated non-metallic ABS |
| Insulation | Class II (double-insulated) |
| Potting | Solid epoxy resin, hermetically sealed |
| Voltage Boost | 104 V & 208 V included |
| Soft-Start | Included |
| Leads | AWG #10 CU, color-coded |
| Mounting | Central carriage bolt — deck or bulkhead |
| Certifications | UL Listed E509703, Ignition Protected |
| Origin | Made in USA |
Electrical & Installation Notes
Overload Protection Isolation transformers must be protected from overload by a dual-pole disconnect circuit breaker installed between the shore cable entry point and the transformer’s primary side. The breaker rating must be equal to or less than the transformer continuous current rating (30 Amp for a 120 V MP3.6). D-curve (delayed action) circuit breakers are recommended.
Marinepuck Installation: MarinePuck Brochure
Inrush Current Toroidal transformers can produce a brief inrush current surge at startup. Using a D-curve breaker is the preferred solution. An NTC thermistor can also be used in series with the primary winding if needed.
Double Insulation Marine-Puck transformers are encapsulated inside a cup-shaped plastic enclosure, providing true double insulation. The ABS case combined with solid epoxy potting eliminates shock and fire hazards from loose conductors and prevents seawater ingress.
| Shore Power | Boat’s Electrical Panel | Electrical Schematics | |
|---|---|---|---|
| Single MP | Dual MP | ||
| 120V 30A (3 wires) |
120V | 120V/120V | NA |
| 120V/240V | 120V/240V | NA | |
| 240V 50A (4 wires) |
120V | S240V/120V | NA |
| 120V/240V | S240V/240V | D240V/240V | |
Mounting
The Marine-Puck mounts on top of or below a deck or bulkhead using a single central carriage bolt with flat washer, split lock washer, and hex nut. Input and output wiring may exit from the rear through the mounting surface or radially through the lower rim in any orientation.
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