Around the late 80s BMW decided to close its marine division. Mercury Marine took over BMW Marine and continued to manufacture the engines in the same guise initially. Small changes were made to the engines and their designations. VM Motori increased the capacity of the HRH 636 3.6 litre engine to 4.2 litres by increasing the bore and stroke to 94 x 100. Mercury gave this engine a new designation of D254 Turbo AC (254ci).
The horse power of this engine rose to 220 hp as opposed to the 150 and 190 hp BMW diesels. The power delivery and torque of this engine was much smoother than the BMW diesels and the engines also ran more smoothly. The same block was supplied in industrial and automotive applications.
All the engine parts are readily available for the Mercury Marine engines but heat exchangers are now out of production and difficult to obtain. Please contact the office by email or telephone if you need help.