The original design from Einar Ohlson specified a VOLVO MD2B to be fitted for the OHLSON 38. The MD2 was introduced by VOLVO in 1964 with 15 HP (European). The VOLVO MD2 was VOLVO's first true marine engine and has a reputation both for fuel efficiency and reliability. The MD2 is a simple, two cylinder diesel engine. In 1967, VOLVO developed from this the MD2A which was brought up to 16.5 HP. In 1970 VOLVO developed this engine into what became the MD2B, giving 25hp at 2,500 rpm, manufactured until 1976. The initial dynastart (a belt-driven combination of a DC power generator and starter motor) was changed to a starter motor and a separate 35 amps alternator. Later boats have been fitted out with the newer developments of this engine. Capacity of this engine was 1.12 l (from its previous 890 cc) by boring up the cylinders from 79.37 mm to 88.9 mm.

An excellent article on the overhaul of the VOLVO MD2B has been published in 1997 in Practical Boat Owner. These articles are available on request to Practical Boat Own in the UK. In case you cannot find the article please send in a request.  

The engine compartment on the OHLSON 38 is reasonably spacy and allows to fit engines of other sizes or makes. We have now fitted a Bukh DV36 which replaces the legendary MD3B initially built into the boat. Weight of both engines is the same. Today various engines from Yanmar, Beta and Volvo Penta have been installed in sizes around 30 HP, which should not have proven to be a problem given the size of the engine compartment. There usual dimensions range around 490mm/19" overall width, their feet to a maximum of 410 mm/16" apart.