Abstract: A combustion engine driven liquid heater wherein an internal combustion engine is utilized as the primary liquid heating energy source. The internal combustion engine is submerged in a container of liquid to be heated and is adapted to operate in its submerged condition. A friction heater is also submerged in the liquid to be heated and is driven from the internal combustion engine. In addition, the exhaust system of the internal combustion engine is caused to meander throughout the liquid before exhausting to the atmosphere. The liquid thus heated is then flowed through a heat dissipation or radiation system such as might be found in the conventional home. Thus, not only is the heat of combustion and all the heat produced by the power of combustion fully utilized to heat the liquid, but in addition, the heat given off due to friction of engine parts is also captured and fully utilized.