Fleming 55 electric repower: motor, battery and cable sizing

The Fleming 55 is a 17 m monohull with a 15.5 m waterline and 30,754 kg displacement. From those figures, the configurator's sizing model puts an electric conversion at 40 kW and 128 kWh on a 96 V system.

Boat data: Fleming — Fleming 55 specification, checked 23 October 2026

Motor power

40 kW

28.4 kW needed at 7 kn

Battery pack

128 kWh

2 h at full rating, with reserve

DC design current

772 A @ 96 V

cabling burden: very heavy

Range on that pack

14 nm

at 7 kn

Open the Fleming 55 in the configurator Compare motors for 40 kW

The boat

Length: 16.99 m
Waterline length: 15.5 m
Beam: 4.88 m
Displacement: 30,754 kg
Hull: Monohull
Builder: Fleming Yachts
Original engine: Twin Cummins QSC 8.3 — 500 hp each, shafts

Power needed by speed

Speed	Shaft power
3 kn	3.9 kW
4 kn	7.1 kW
5 kn	11.9 kW
6 kn	18.7 kW
7 kncruise target	28.4 kW
8 kn	42.2 kW
9.6 knhull speed	77.2 kW

The configurator's power-per-tonne heuristic, not a tank test — real boats vary by about ±25% with hull form, fouling, sea state and propeller. Near hull speed the power climbs steeply.

48 V or 96 V

48 V system

1389 A

design DC current · cabling burden very heavy · 400 mm² for a short run

96 V systemconfigurator's choice

772 A

design DC current · cabling burden very heavy · 400 mm² for a short run

Motor lines that cover 40 kW at 96 V

ePropulsion

I-Series (I-10, I-20, I-40)

Inboard · 10–40 kW · 96 V class

From our motor comparison, matched by power and system voltage only — check drive type and fit with the maker.

What these numbers assume

The published displacement. Your boat loaded for cruising is heavier — use your own figure in the configurator.
Cruise target of 7 kn, which is 75% of the 9.6 kn hull speed.
A shaft drive, as the source states.
A pack sized for 2 hours at the motor's full rating, 15% reserve and 80% usable depth of discharge.
Displacement is Fleming's minimum operating condition (30,754 kg); loaded, Fleming gives 36,368 kg. Length is the hull length — 18.50 m including swim step and anchor platform. Its twin 500 hp engines are sized for much faster running than this page covers: these figures are for displacement speed only.

Fleming 55

Common questions

How many kW does a Fleming 55 need for electric propulsion?+

About 28.4 kW to hold 7 knots — 75% of its 9.6-knot hull speed — so the configurator suggests a 40 kW motor. Power rises steeply above that: about 77.2 kW at hull speed. These are estimates from the boat's published waterline length and displacement; real boats vary by roughly ±25%.

What size battery does a Fleming 55 need?+

The configurator sizes about 128 kWh of LiFePO4 for 2 hours at the motor's full 40 kW rating, with a 15% reserve and 80% usable depth of discharge — about 14 nautical miles at 7 knots. Cruising below full power stretches that.

Should a Fleming 55 use 48 V or 96 V?+

At 40 kW the design DC current is about 1389 A at 48 V (cabling burden: very heavy) and about 772 A at 96 V (very heavy). The configurator picks 96 V for this boat: it stays on 48 V unless the 48 V current reaches its "very heavy" level.