The engine manual is the authority. This planning table shows the categories owners commonly need to schedule, not universal intervals.
| Timing trigger | Typical work to check against the manual |
|---|---|
| Before use | Fluids, leaks, raw-water flow path, belt, bilge, controls, fuel |
| First service after installation or major work | Oil and filter, mounts, alignment, belts, leaks, fasteners and model-specific inspections |
| Regular engine-hour service | Oil, filters, water separator, belt, impeller and general inspection as specified |
| Annual or calendar service | Items that age even with few hours: oil, coolant tests, hoses, anodes, drive, batteries, exhaust and corrosion |
| Longer interval | Valve clearance, injectors, heat exchanger, exhaust elbow, coolant replacement, timing components where fitted |
| Haul-out | Propeller, shaft or saildrive, seals, bearing, anodes, coating, intake and through-hulls |
Use whichever limit arrives first: hours or time. A boat that runs only 30 hours a year still experiences condensation, corrosion, rubber ageing, microbial fuel growth and coolant depletion.
Record the exact product and part number used. “Oil changed” is weaker evidence than “4.2 L of specified grade, filter number, date, hours, sample appearance and next due point”. Keep receipts and photographs, especially for saildrive diaphragms, exhaust work and repower installations.
After service, run the engine, inspect for leaks, recheck levels and review disturbed items. Many failures occur because a filter seal doubled, a seacock stayed closed, a hose clamp was forgotten or oil level was checked before the filter filled.