Selecting an engine for a yacht

The table below shows an approximate guide for matching engine size to a displacement yacht. We have assumed that the yacht is intended to reach the maximum speed permitted by its hull design. This assumption does not hold for fast racing yachts, where the engine is used only for maneuvering and can be considerably smaller than the calculator suggests. The same applies to family cruising, where we often want around a 30% power reserve for safety reasons.

Ideally, you should seek advice from the boatyard or boat designer regarding the best engine power and propeller selection. For the best engine match, please contact us at info@dieselair.pl. Based on the data you provide, we will precisely select the propeller and engine for you.

The general rule states that for cruising yachts, at least 5 hp should be allowed for each tonne of displacement. On the Baltic Sea, we can often opt for a smaller engine, due to the absence of tides and currents. For vessels operating on rivers, particularly rivers in Western Europe, the ratio can be as high as 7 hp per tonne of displacement, due to generally stronger currents. In our Masurian Lake District or Warmia region, considerably smaller engines are sufficient compared to the Baltic, owing to the yacht's shallower draft, lack of a keel, and generally lower displacement per meter of length than is the case with seagoing yachts.

To calculate your yacht's maximum speed yourself, you can use the following formula:

hull speed in knots (for displacement hulls) = 1.3 (or 1.4 for slender hulls) × √ waterline length (in feet)

Please choose your engine carefully. Neither Beta Marine Limited nor Diesel Air accepts any liability for an incorrect engine selection.

The above guidelines do not apply to engine selection for catamarans, semi-displacement vessels, or planing vessels. In such cases, please contact us at: info@dieselair.pl.