Isotemp, part of Indel Webasto Marine, specializes in marine water heaters and hot-water systems for boats and yachts. The range is designed for onboard installations where compact dimensions, reliable hot-water supply, corrosion resistance, and efficient use of available energy are important.
Isotemp water heaters are available in different capacities and installation formats to suit a wide range of vessels. Depending on the model and system configuration, water can be heated using an electric heating element, engine coolant, or a combination of available heat sources.
At Yacht-Supply24.com, we supply Isotemp water heaters, accessories, and replacement parts and can assist with product selection, compatibility checks, and identification of components for existing onboard hot-water systems.
Send us your request if you need help selecting the correct Isotemp water heater or replacement part.
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1-2 weeks delivery time The Isotemp 601523S000003 Slim 15L marine water heater uses a 115V/750W immersion element and a stainless-steel 4-gallon tank with an integrated mixing valve. With the heater and heat exchanger positioned low in the cylinder, it delivers uniform water heating, while optimized inlet/outlet geometry reduces cold-water mixing for higher effective hot-water capacity in compact installations. |
$ 1,016.35
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1-2 weeks delivery time The Isotemp 601531S000003 Slim 15L marine water heater features a 4-gallon stainless steel tank, a 230V/750W immersion heater, and an integrated mixing valve for stable outlet temperature. The heat exchanger and heating element are positioned low in the tank for uniform heating, while dedicated inlet/outlet geometry minimizes cold-water mixing for maximum usable hot-water capacity in compact onboard installations. |
$ 854.34
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1-2 weeks delivery time The Isotemp 602023S000003 Slim 20L marine water heater features a 5.3-gallon stainless-steel tank with a 115V/750W immersion heater and an integrated mixing valve. With the heater and heat exchanger installed at the lowest point for even heat distribution, and optimized inlet/outlet geometry to reduce cold-water mixing, the unit delivers maximum usable hot-water capacity for compact onboard systems. |
$ 1,026.82
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1-2 weeks delivery time The Isotemp 602031S000003 Slim 20L marine water heater features a 5.3-gallon stainless-steel tank with a 230V/750W immersion heater and an integrated mixing valve. With the heating element and heat exchanger mounted low in the cylinder, the unit provides uniform heating, while optimized inlet/outlet geometry reduces cold-water mixing to deliver maximum usable hot-water volume in compact onboard installations. |
$ 918.92
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1-2 weeks delivery time The Isotemp 602423B000003 Basic 24L water heater features a 6.4-gallon stainless-steel tank, a 115V/750W immersion heater and an integrated mixing valve. With the heating element and heat exchanger installed low in the tank for uniform temperature distribution, and inlet/outlet geometry designed to reduce cold-water mixing, it provides high hot-water output in compact marine installations. |
$ 1,075.72
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1-2 weeks delivery time The Isotemp 602431B000003 Basic 24L marine water heater features a 6.4-gallon stainless-steel tank, a 230V/750W immersion heater, and a built-in thermostat-controlled mixing valve. With the heater and heat exchanger mounted at the tank’s lowest point for uniform heating, and optimized inlet/outlet geometry to reduce cold-water mixing, it delivers high hot-water output in a compact footprint. |
$ 904.19
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1-2 weeks delivery time The Isotemp 602431BD00003 Basic 24L water heater features a 6.4-gallon stainless-steel tank with a 230V/750W immersion heater, dual heat-exchange coils, a dual thermostat system and an integrated mixing valve. This configuration increases heating efficiency, supports multiple engine-circuit connections and ensures uniform water temperature with reduced cold-water mixing. |
$ 1,177.01
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1-2 weeks delivery time The Isotemp 602523S000003 Slim 25L marine water heater features a 6.5-gallon stainless-steel tank with a 115V/750W immersion heater and an integrated mixing valve. With low-mounted heating components for uniform temperature distribution and optimized inlet/outlet geometry to limit cold-water mixing, it provides maximum hot-water output in compact Slim-series installations. |
$ 1,093.19
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1-2 weeks delivery time The Isotemp 602531S000003 Slim 25L marine water heater features a 6.5-gallon stainless-steel tank with a 230V/750W immersion heater and an integrated mixing valve. With the heating element and heat exchanger mounted at the lowest tank point and optimized inlet/outlet design to reduce cold-water mixing, it delivers maximum usable hot-water capacity in a compact Slim-series footprint. |
$ 999.53
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1-2 weeks delivery time The Isotemp 602531S000026 Slim 25L deflagration-proof marine water heater features a 6.5-gallon stainless-steel tank, a 230V/750W immersion heater, and an integrated mixing valve. Designed for hazardous or enclosed onboard spaces, it provides explosion-resistant construction, uniform heating via a low-mounted element and heat exchanger, and optimized inlet/outlet geometry to reduce cold-water mixing. |
$ 2,326.06
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1-2 weeks delivery time The Isotemp 6025B1S000003 Slim 25L marine water heater features a 6.5-gallon stainless-steel tank with a high-output 230V/1200W immersion heater and an integrated mixing valve. Its low-mounted heating components and optimized inlet/outlet geometry ensure uniform water heating and reduced cold-water mixing, delivering maximum usable hot-water performance in compact marine installations. |
$ 1,236.38
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1-2 weeks delivery time The Isotemp 603023B000003 Basic 30L marine water heater offers an 8-gallon stainless-steel tank, a 115V/750W immersion heater and an integrated mixing valve. With both heating components positioned low in the tank and optimized inlet/outlet geometry to reduce cold-water mixing, it provides uniform heating and high-output performance for medium-size onboard hot-water systems. |
$ 1,173.51
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1-2 weeks delivery time The Isotemp 603031B000003 Basic 30L marine water heater offers an 8-gallon stainless-steel tank with a 230V/750W immersion heater and a built-in mixing valve. With low-mounted heating components and optimized inlet/outlet geometry that reduces cold-water mixing, it provides uniform heating and high effective hot-water output for medium-size onboard installations. |
$ 1,149.07
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1-2 weeks delivery time The Isotemp 604023B000003 Basic 40L marine water heater features an 11-gallon stainless-steel tank with a 115V/750W immersion heater and an integrated mixing valve. With low-mounted heating components for even temperature distribution and inlet/outlet geometry designed to reduce cold-water mixing, it provides reliable medium-capacity hot-water performance for onboard systems. |
$ 1,197.96
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1-2 weeks delivery time The Isotemp 604023BD00003 Basic 40L marine water heater features an 11-gallon stainless-steel tank with a 115V/750W immersion heater, dual heat-exchange coils and an integrated mixing valve. A low-mounted heater and double-coil layout ensure fast, uniform heating, while optimized inlet/outlet design limits cold-water mixing to maximize usable hot-water volume. |
$ 1,515.78
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1-2 weeks delivery time The Isotemp 604031B000003 Basic 40L marine water heater features an 11-gallon stainless-steel tank, a 230V/750W immersion heater and an integrated mixing valve. With heating components mounted at the lowest point for uniform temperature distribution and optimized inlet/outlet geometry that reduces cold-water mixing, it delivers high hot-water output for larger onboard systems. |
$ 1,008.78
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1-2 weeks delivery time The Isotemp 604031BD00003 Basic 40L marine water heater features an 11-gallon stainless-steel tank, a 230V/750W immersion heater, double heat-exchange coils, dual thermostats and an integrated mixing valve. With low-mounted components for uniform heating and optimized inlet/outlet geometry that reduces cold-water mixing, it delivers high hot-water output and multi-circuit compatibility for demanding marine systems. |
$ 1,484.35
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1-2 weeks delivery time The Isotemp 6040B1B000003 Basic 40L marine water heater features an 11-gallon stainless-steel tank with a high-output 230V/1200W immersion heater and an integrated mixing valve. With low-mounted heating components for uniform water temperature and inlet/outlet geometry that reduces cold-water mixing, it offers fast heat-up performance and high usable hot-water capacity for medium and large vessels. |
$ 1,264.32
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What are Isotemp marine water heaters designed for?
Isotemp marine water heaters are designed to provide a reliable hot-water supply on boats and yachts. Depending on the model and installation, water can be heated using an electric heating element, engine coolant through an internal heat exchanger, or both heat sources.
Different tank sizes and installation formats are available to suit a wide range of vessels, from compact boats to larger yachts with higher hot-water demand.
What is the difference between Isotemp Slim, Basic, and other water heater designs?
Different Isotemp water heater ranges are designed for different installation requirements. Slim models are intended for spaces where a narrow cylindrical tank is easier to accommodate, while other designs provide different capacities, shapes, and mounting options for engine rooms, lockers, and technical spaces.
The best choice depends on available space, required hot-water capacity, mounting orientation, electrical supply, and the layout of the vessel’s cooling and plumbing systems.
How does an Isotemp water heater use engine heat?
Many Isotemp water heaters include an internal heat exchanger connected to the engine cooling circuit. While the engine is running, hot coolant passes through the heat exchanger and transfers heat to the freshwater stored inside the tank.
This allows the vessel to produce hot water using heat that is already available from the engine, reducing the need to rely entirely on electric heating while underway.
What is the purpose of the electric heating element in an Isotemp water heater?
The electric heating element provides an alternative way to heat the water when engine heat is not available, such as when the boat is connected to shore power. A thermostat controls the heating cycle to maintain the water within the designed operating range.
The electrical rating and supply voltage must match the specific Isotemp model and the vessel’s electrical system.
What does the mixing valve do in an Isotemp water heater system?
A mixing valve blends hot water from the heater with cold water before it is delivered to the onboard plumbing system. This helps reduce the outlet temperature to a more comfortable level and allows the stored hot water to be used more efficiently.
Correct adjustment and installation of the mixing valve are important for maintaining a stable and practical hot-water temperature at taps and showers.
How can I choose the correct Isotemp water heater for my boat?
Selection should be based on required tank capacity, available installation space, mounting orientation, vessel voltage, electrical power supply, engine coolant connections, and expected hot-water consumption.
For replacement projects, the dimensions, hose connections, electrical rating, and mounting arrangement of the existing heater should also be compared before selecting a new model.
How can I identify the correct Isotemp replacement part?
The best starting point is the water heater model, product number, tank capacity, voltage, and original spare-part reference where available. Photographs, dimensions, connection sizes, and details of the existing installation can also help identify the correct component.
Compatibility should always be confirmed before ordering heating elements, thermostats, valves, fittings, or other service parts.