Side-Power SP75 Bow Thruster connections

This walkthrough covers the original 12 V SP 75 T, using Sleipner's archived installation/user manual. It does not borrow ratings from the later SP75Ti or SE80. Confirm the motor plate and revision on an older or rebuilt thruster. The manual PDF is hosted by a boat-document archive; printed pages are used here because its page numbering differs from the PDF index.

Printed page 28 lists 480 A for the ordinary 12 V SP75T circuit, with separate 300 A remote-feed guidance only for the illustrated extra bow-battery arrangement. That 300 A row does not rate the motor itself at 300 A. The previous catalog's 260 A operating estimate was unsupported by this table.

The battery, positive isolator, protection and motor return form a dedicated circuit. The manual requires an accessible main switch and slow protection able to carry the stated operating current for at least five minutes. It does not establish the catalog's former blanket 500 A ANL claim; obtain the appropriate fuse characteristic for the installed revision and cable system.

The page 28 table uses total positive-plus-negative length and battery cold-cranking capability. For the ordinary 12 V row up to 7 m, it gives 50 mm² cable and 550 A DIN CCA minimum. Larger/longer installations use different rows. Lithium Ah capacity alone does not show that a BMS can sustain this motor load. The planner can cap its calculated cable current at a lower battery terminal limit; a result below 480 A is not approval for this motor circuit. In particular, a single 400 A-rated battery does not establish adequate continuous supply capability.

Page 28 maps battery negative to A1 and positive to the marked positive connection. Its tightening instruction calls for holding the inner nut to prevent stud rotation, with 15 Nm maximum. Pages 30–33 show the control connector, electronic control box, reversing solenoids and thermal switch, omitted by the two-pin canvas representation. Preserve those protections and controls.

Printed page 36 limits continuous operation to approximately three minutes, with roughly 10% usage over time depending on conditions. Thermal shutdown is a limit, not a manoeuvring strategy. Do not plan continuous position-holding against wind or current.

Commission with the tunnel and propellers clear, verify direction, loaded voltage and emergency isolation, and follow the manual's oil-system, anode and mechanical checklist. Never run a prolonged dry test or work near the propellers with power available. Starting current remains unverified; the obsolete 380 A surge estimate has been removed rather than presented below the documented running current.