Start by describing the failure precisely. “Engine dead” could mean the panel is dark, starter does not turn, starter turns slowly, engine cranks normally but does not fire, or engine starts and stops. Each points to a different branch.
The diagnostic sequence
- Make the boat safe. Maintain steerage, sail, anchor or call for assistance.
- Note alarms, gauge values, smoke, smell, sound, rpm and sea conditions.
- Ask what changed. Recent filter work, refuelling, grounding, battery work and a newly closed seacock are high-value clues.
- Perform visual checks before dismantling.
- Divide the system: electrical, fuel, air, cooling, exhaust, internal mechanical or propulsion load.
- Test the simplest safe hypothesis with a measurement.
- Change one thing at a time and record the result.
- Confirm the repair under controlled load and recheck for leaks.
Avoid bypassing alarms, shorting terminals, spraying starting fluid or opening high-pressure fuel systems. These actions can injure people and create additional faults.
Choose the closest symptom page: will not crank · cranks but will not start · starts then stops · loses power · overheats · smoke · vibration