24 QUESTIONS

Faults and Fixes

1. 01

   Why do batteries get hot?

   A hot battery is almost always the symptom of another fault: overcharging, a loose terminal or an internal short. A hot terminal looks perfectly sound to the eye but shows as a distinct point on a thermal camera.

   This is the first step towards an electrical fire, which is why the battery compartment is scanned under load during a survey rather than merely inspected.

2. 02

   Why have my navigation lights stopped working?

   At sea most faults are in the circuit rather than the bulb: a damp holder, an oxidised terminal or a corroded cable end. Replacing the bulb is therefore usually a temporary fix.

   Navigation lights are not a convenience item but your visibility at night, so they are operated and confirmed during a survey rather than assumed to work.

3. 03

   Why is my solar panel not producing its rated output?

   The rated figure describes laboratory conditions; real output on a boat is set by shading, angle, temperature and the type of charge controller. A single shadow line from a mast or shroud can pull down an entire series-connected string.

   Declaring the panel faulty before measuring is premature — in most cases the installation rather than the panel is the limiting factor.

4. 04

   The air conditioning is not cooling or heating — what should be checked?

   On a seawater-cooled system the first place to look is the water circuit rather than the gas: seacock, strainer and pump. A circuit with reduced flow puts the compressor into protection, so the unit appears to run without cooling.

   Measuring the air coming out of the vent with a thermal camera separates a gas problem from a flow problem before anything is dismantled.

5. 05

   Why does my lithium battery stop accepting charge or trip the BMS?

   A cut-off is usually the BMS’s decision rather than a battery failure: cell imbalance, a temperature limit or an incompatible charge profile. A profile set for lead-acid causes interruptions on lithium.

   This is why a conversion has to change the charging side as well as the batteries. Replacing cells while leaving the alternator regulation alone reproduces the fault.

6. 06

   Why does my chartplotter or VHF fail to start or freeze?

   Most electronics faults are in the supply and the data network rather than the unit: voltage drop, an oxidised connector or a conflict on the NMEA bus. Replacing the device can simply move the problem.

   In a helm survey every unit is powered up and confirmed to be receiving data, which is what separates "present" from "working".

7. 07

   Why are my trim tabs not working and the boat listing?

   One-sided failure is almost always hydraulic or electrical: the pump, the actuator or the cabling. The consequence is not only comfort — uneven trim spoils steering response at speed.

   Both sides are therefore operated independently during a survey rather than judged from the boat’s attitude alongside.

8. 08

   Why will the gearbox not engage ahead or astern?

   Before blaming the internals, look at the control side: cable adjustment, the coupling and gearbox oil level. Those three account for most cases.

   Where the internals are involved, metal particles show in the oil — which is why the gearbox oil is inspected as part of the engine room survey rather than only the shift action.

9. 09

   Why does my generator drop out or stop under load?

   Dropping under load means the engine cannot find enough air, fuel or cooling: a blocked fuel filter, a dirty air filter or low raw water flow.

   A diagnostic tool can be connected to the generator as well; reading the fault record and running hours usually points straight at the cause instead of working through the possibilities.

10. 10

    How is water or diesel bug cleaned out of a fuel tank?

    Diesel bug grows at the interface between water and fuel, so the answer is not to add biocide but to remove the water first. Any treatment applied without taking a sample from the tank bottom is incomplete.

    The problem is more common in lightly used boats, which is why tank bottoms and filters are inspected specifically during a survey rather than only when a fault is reported.

11. 11

    My hydraulic steering has gone heavy or slack — what should I do?

    Slackness usually means air in the system; heaviness means either a leak or mechanical friction. Both leave traces at the rudder stock and the seals.

    Steering is operated under load during a survey and stock clearance is measured, because loss of steering at sea is among the most serious failures a boat can suffer.

12. 12

    The batteries are not charging — how do I identify an alternator fault?

    Measurement separates an alternator fault from a battery fault: if the voltage at the battery terminals does not reach the expected range with the engine running, the problem is on the charging side. Belt tension and the regulator are part of the same chain.

    That measurement is taken during a survey and the connections are additionally scanned with a thermal camera, since a hot joint produces the same symptom as a failing alternator.

13. 13

    The engine temperature spikes underway — what should I do first?

    Reduce revs and, if necessary, shut down; pushing a hot engine turns a cooling fault into head and gasket damage. Then check the raw water circuit: seacock, strainer, impeller.

    A single overheating event changes the remaining life of an engine and leaves an entry in the ECU. That record is read during a survey — it is one of the most valuable pieces of history a buyer can get.

14. 14

    Why does the engine hunt or stall at idle?

    Idle hunting is usually on the fuel side: an air leak at a connection, a filter beginning to block or injector imbalance. On electronic engines the fault record often gives the cause directly.

    A cylinder balance test taken with a diagnostic tool shows which cylinder is falling behind as a number rather than as an impression.

15. 15

    The windlass clicks but does not turn — what is wrong?

    The click tells you the control signal arrives and the motor does not turn: the fault is either in the power circuit (cable size, fuse, oxidised terminal) or a mechanical seizure.

    A windlass draws very high current, so even a small connection resistance is enough to stop it turning. It is operated under load during a deck survey for that reason.

16. 16

    How do I clear a blocked marine toilet?

    Most blockages are not in the toilet but in scale and sediment built up in the discharge line, so check the hose run before dismantling the pump.

    Forcing a blockage can split a hose or a union, at which point the problem changes from a blockage to water ingress. The discharge line and its fittings are inspected separately during a survey.

17. 17

    How much should a traditional stern gland drip?

    A traditional gland should drip slightly while running — that drip cools the bearing — and should not drip when stopped. Excessive dripping means it needs adjustment; no drip at all means it is over-tightened and running hot.

    The drip rate is counted both running and stopped during a survey, and the box temperature is read with a thermal camera. Both numbers go in the report.

18. 18

    Why does a fuse keep blowing on the panel?

    A fuse that keeps blowing is not a fault but a warning: there is a leak or an overload on the circuit. Fitting a higher-rated fuse breaks the protection chain and burns the cable instead.

    The correct approach is to divide the circuit and find the source. During a survey, fuse ratings are also checked against cable sizes — a mismatch is a finding in its own right.

19. 19

    Why does my water pump cycle on and off?

    Cycling usually comes from lost air pressure in the accumulator or air entering the system. Replacing the pump does not address either.

    A pump that cycles constantly drains the batteries and wears itself out, so the plumbing is observed under pressure during an interior survey rather than simply switched on.

20. 20

    The bilge pump runs continuously — what should I do?

    A continuously running bilge pump is news rather than a fault: the boat may be taking water. The first step is to establish whether the water is salt or fresh — salt points to the hull and skin fittings, fresh to the cooling circuit or plumbing.

    A stuck float switch produces the same symptom, so the two have to be told apart before anything else. That single test decides where you look next.

21. 21

    When should the raw water impeller be replaced?

    An impeller fails suddenly rather than gradually, and the broken vanes block the heat exchanger — so replacement is done on a schedule rather than on symptoms. Every broken vane must be accounted for when it is changed.

    Impeller condition and the raw water circuit are checked during an engine room survey for exactly this reason: the failure mode gives no warning.

22. 22

    Why does my engine produce black smoke?

    Black smoke means fuel is not burning completely: overload, a blocked air filter, a turbo problem or injector imbalance. Overload often comes from the wrong propeller pitch — the engine cannot reach its rated revs.

    Diagnostic reading and a cylinder balance test separate a fault in the engine from a fault in the load, which are treated very differently.

23. 23

    Why does my diesel produce white smoke?

    White smoke can be normal on a cold engine; if it continues once warm, unburnt fuel or water entering the combustion chamber are the candidates. The second is a serious problem at the gasket or head.

    Coolant level, oil condition and ECU records are read together to tell the two apart before anything is dismantled.

24. 24

    Why will my engine not crank?

    Most causes are in the circuit rather than the engine: battery voltage, the main switch, the starter relay or an oxidised terminal. A click points to the power circuit; complete silence points to the control circuit.

    During a survey the battery bank is measured and the connections are scanned with a thermal camera, since a high-resistance joint produces exactly this symptom intermittently.