PLEASE NOTE: The hot water systems must be installed by a licenced electrician. This product is supplied with the "white" power lead plug cut off as it does not meet the Australian shape/standard.  A "black" lead with an Australian plug and crimp fittings is provided in the box for the installation.

The Isotemp SLIM line of Stainless Steel Marine Water Heaters comes with brushed stainless steel cover as well as innovative internal design. The Slim models are characterized by a smaller diameter (12 inches) and longer length.

Isotemp SLIM Stainless Steel Marine Water Heaters are specifically designed for use in the demanding marine environment.  Isotemp SLIM features a brushed stainless steel cover and a 316-grade stainless steel inner tank that is backed by a 5-year limited warranty against leakage due to corrosion or manufacturing defect.

Isotemp Stainless Steel Water Heaters achieve the highest capacity by optimising the position of the engine water heat exchanger as well as the electrical immersion heater. These are positioned in the lowest part of the tank where the water is coldest in order to ensure an equal heating of all the water in the tank. The water inlets and outlets are specially designed to minimise the mixture of cold and hot water.

All Isotemp tanks come standard with the innovative Isotemp Temperature Control Safety Mixing Valve which protects users from scalding hot water.  Water heated with engine heat exchangers can be heated to 190 degrees or more which can scald those unfamiliar with boat water heaters.  Water will also be heated to 160+ degrees with just the electric heating element alone. By adjusting the valve, the Isotemp thermostat-controlled mixing valve mixes the boat’s water with the hot water to deliver the temperature you want at the faucet. This mixing action also speeds recovery time and extends the volume of hot water you get from a smaller tank.


  • Extra long, corrugated coils for high heat exchange efficiency
  • Special 7.0 bar / 100 psi safety valve
  • Simple winter drain
  • Ultra-thick insulation for lowest temperature loss
  • Electrical plug and play immersion heating element, especially designed to heat also the water at the bottom of the tank
  • Thermostat mixing valve protects against scalding and delivers consistent temperatures at the faucet
  • Standard 750 watt immersion heating element heats water quickly but will not overload generators or dock breakers
  • Robust design
  • Water tank in 316 grade stainless steel
  • External cylinder in stainless steel
  • Stable fixing feet in stainless steel
  • Horizontal deck or bulkhead mounting
  • Vertical bulkhead mounting (valves down)


  • Volume (L): 25
  • Dimensions L x ø D* (mm): 765 x 295 (* Including thermostat mixing valve)
  • Weight (kg): 12


SKU ISO.602531S000003
Model # KTH602531S000003
Brand Isotemp
Shipping Weight 14.0000kg
Unit Of Measure ea

Great customer service

By: on 9 November 2022
I purchased an Isotherm 25 litre slim line which on. Opening the box had some damage. I took photos of the damage and emailed outback marine and within an hour I had a response and a ticket to investigate the issue. The very next day I was dispatched another unit without a quibble. This is rare these days and I couldn’t be happier. The customer service is second to none and I would not hesitate to recommend Outback Marine there service and there products. I haven’t had a chance to instal it yet, but the new unit is immaculate. A happy customer.

Write a product review