Question 1

The impeller has failed. You are 400m from the harbour entrance. How long does an impeller change typically take and what do you need?

Accepted Answer

Typically 15–30 minutes with the right tools and a spare: close the raw water seacock; remove the pump cover screws; extract the impeller with impeller pullers or long-nose pliers; fit the new impeller with blades bent in rotation direction; refit cover with new gasket; open seacock and check for water flow on restart An impeller change is a practical seamanship skill. Tools required: correct screwdrivers or Allen keys for the pump cover, impeller pullers or large pliers, replacement impeller, spare gasket or sealant, and waterproof grease. With practice: 10-15 minutes. However, 400m from a harbour entrance is a dangerous time to lose propulsion — you should have been monitoring exhaust water on every engine start. Meanwhile: sail or anchor.

Question 2

You turn the key. No cranking sound at all — complete silence. What is the most likely fault category and what do you check first?

Accepted Answer

Electrical: check battery voltage (battery monitor or multimeter); check main battery isolator switch is ON and set to the correct bank; check the engine battery is not flat; check the kill/stop control is in the RUN position No crank = electrical fault (unless the decompressor or stop control is engaged). Sequence: 1) Is the battery isolator ON and on the correct bank? 2) Is battery voltage above 12V (10.5V minimum for cranking)? 3) Is the kill/stop control fully in RUN? 4) Is the neutral safety switch in neutral? Do not proceed to fuel diagnosis until you have confirmed electricity is reaching the starter motor.

Question 3

The battery isolator has two banks (1 = House, 2 = Engine, BOTH). The switch is on BOTH. The voltage reads 11.8V. What does this tell you and what do you do?

Accepted Answer

11.8V is borderline for reliable starting — switch to Bank 2 (engine bank only) which may have more charge; reduce all electrical loads; try cranking on the dedicated engine bank A diesel starter motor needs high current (200–500A peak). 11.8V under no load may drop to 9–10V under cranking load on BOTH banks — below the starter's cut-out. Switch to the dedicated engine bank, turn off navigation instruments and VHF to reduce parasitic load, and crank in short bursts (10 seconds max) to avoid overheating the starter. If still no crank, check the starter solenoid wire and starter motor itself.