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Diesel Marine Propulsion Engines & Marine Generating Sets

Rough Guide to Engine Selection for Yachts

Use this table as a ‘rough guide’ only when selecting the size of engine you require for displacement hulls / sailing yachts. Our assumption is that you will wish to reach maximum hull speed of your yacht, and therefore require a suitable engine to achieve this. This assumption may not be correct if you have a racing yacht and only want limited power to reach your moorings; or conversely you do motor sailing with your family and wish a 30 percent safety factor.

You should always talk to the hull designer and boat builder for their recommendations of engine power and propeller size (as theoretically they have specified the boats designed performance / hull speed) – the propeller supplier then specifies a suitable propeller to achieve the boats designed performance (based upon engine brake horse power and rpm) – we then supply the required engine. This basis will never be an exact science as this calculation requires a clean and polished hull,  no ‘windage’ (being blown sideways or backwards) and a calm sea  (some heavy seas can simply stop a boat).

  • A generally accepted rule of thumb for displacement hulls is about 4 bhp per ton for cruising yachts
  • Maximum hull speed in Knots (for displacement hulls) = 1.3 (or 1.4 for a sleek hull) x √ Water Line length (in feet)
  • Beta Marine Limited will not accept any responsibility for incorrect engine selection

Customer Input

Water Line Length in Feet:

Results

Approx. Calculated Boat Speed in Knots:

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EngineBHPYacht Displacement Weight in TonnesLWL in Feet (Water Line Length)
Beta 1010 bhp at 3,000 rpm1 - 222 - 24
Beta 1413.5 bhp at 3,600 rpm2 - 3.524 - 26
Beta 1616 bhp at 3,600 rpm3 - 425 - 28
Beta 2020 bhp at 3,600 rpm4 - 526 - 32
Beta 2525 bhp at 3,600 rpm5 - 627 - 34
Beta 3030 bhp at 3,600 rpm6 - 732 - 36
Beta 3535 bhp at 2,800 rpm8 - 936 - 38
Beta 3838 bhp at 3,600 rpm9 - 1037 - 39
Beta 4545 bhp at 3,000 rpm9 - 1138 - 40
Beta 4343 bhp at 2,800 rpm10 - 1238 - 42
Beta 5050 bhp at 2,800 rpm12 - 1542 - 45
Beta 6056 bhp at 2,700 rpm15 - 1743 - 46
Beta 7575 bhp at 2,600 rpm17 - 2246 - 50
Beta 8583 bhp at 2,800 rpm21 - 2348 - 51
Beta 9090 bhp at 2,600 rpm22 - 2450 - 52
Beta 10599 bhp at 2,600 rpm24 - 2651 - 53
Beta 150147 bhp at 2,800 rpm25 - 3052 - 55

With Catamarans

Ask the Boat Builder / Designer for the recommended engine size. If you have a semi-displacement or planing hull the above guide is not relevant. Please refer to Beta Marine for information.

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