Whale Seaward 11 Gallon Hot Water Heater w/ Rear Heat Exchanger – Stainless Steel – 240V – Model S1250

The Whale Seaward 11 Gallon Hot Water Heater with Rear Heat Exchanger (Model S1250) is a premium marine‑grade electric water heater designed to deliver reliable, abundant hot water for boats, yachts, and RVs. With a generous 11 gallon (42 L) capacity and 240 V power, this unit provides consistent hot water for showers, sinks, and galley use while onboard.

Featuring a rear‑mounted heat exchanger, the S1250 captures and utilizes engine heat to pre‑heat the water as you cruise—reducing reliance on shore power or generators and improving overall energy efficiency. Built with a stainless steel exterior, this heater is engineered to resist corrosion and stand up to the harsh conditions of saltwater environments.

Designed for easy horizontal installation, the Whale Seaward S1250 includes double‑wall heat exchangers, integrated safety controls, a pressure relief valve, and a temperature/pressure drain tube, making it a dependable choice for everyday marine hot water needs.

Dual-Heating Efficiency

The S1250 is engineered to provide hot water under any circumstances:

• Electric Heating: The 1500W heating element operates on 240V AC, providing quick recovery times when connected to a generator or shore power.

• Engine Heat Exchanger: The rear-mounted copper heat exchanger circulates engine coolant, heating the 11 gallons of water to engine temperature for "free" while the vessel is underway.

Key Features

• 304 Stainless Steel Exterior: The polished stainless steel jacket is not just for looks; it provides maximum corrosion resistance against salt air and moisture, outlasting galvanized or painted models.

• Robust Aluminum Tank: The interior tank is built from high-quality aluminum, chosen for its excellent heat transfer and lightweight durability.

• Magnesium Anode Protection: A replaceable magnesium anode rod is included to protect the tank from galvanic corrosion, a critical feature for aluminum-tank longevity.

• Safety First: Equipped with a factory-installed Temperature and Pressure (T&P) Relief Valve and a high-limit thermal cut-out for the electric element.

Applications

• Marine fresh water systems on boats and yachts

• RV and camper hot water needs

• Showers, sinks, and galley water supply

• Engine‑assisted hot water heating systems

• Replacement or upgrade of existing water heaters

Why the S1250 (Rear Exchanger) over the F1250 (Front Exchanger)?

The choice between the S1250 and the F1250 typically comes down to plumbing geometry. If your water heater is mounted against a bulkhead and the engine hoses are coming from behind that wall, the Rear Heat Exchanger on the S1250 allows for a direct connection without looping hoses around the side of the unit. This saves space and reduces the risk of hose kinks.

Installation Pro-Tip:

Since the heat exchanger is located at the rear of this unit, ensure you leave at least 4–6 inches of clearance behind the heater during installation. This provides enough room to service the hose clamps and allows for the natural bend radius of the engine coolant hoses. Never use standard garden hose for the heat exchanger; always use reinforced marine-grade heater hose rated for at least 200°F.