Yanmar 4JH45 service schedule
Inboard diesel ·
18 maintenance items for the Yanmar 4JH45. The engine oil is changed every 250 h or 12 months. When an item has both an hour and a calendar interval, the one that comes first applies.
| Item | Engine hours | Calendar | Rule |
|---|---|---|---|
| Before each start: engine oil, coolant, fuel level, leaks, belt, seawater flow after starting | — | before each use | |
| First service: engine oil and filter, gear oilOnce, after running in. | at 50 h, once | — | |
| Change the engine oil | every 250 h | every year | whichever first |
| Replace the engine oil filter | every 250 h | every year | whichever first |
| Replace the fuel filter element and drain the water separator | every 250 h | every year | whichever first |
| Inspect the seawater pump impeller; replace if worn | every 250 h | every year | whichever first |
| Inspect and replace the engine anodes | every 250 h | every year | whichever first |
| Check the alternator belt tension and condition | every 250 h | every year | whichever first |
| Clean the air intake filter | every 250 h | every year | whichever first |
| Flush the seawater cooling circuit | every 250 h | every year | whichever first |
| Change the marine gear oil | every 250 h | every year | whichever first |
| Change the engine coolant | every 500 h | every 2 years | whichever first |
| Inspect the exhaust mixing elbow for corrosion and carbon | every 500 h | every 2 years | whichever first |
| Inspect fuel, coolant and seawater hoses and clamps | every 500 h | every 2 years | whichever first |
| Check the fuel injection timing and the injectors | every 500 h | every 2 years | whichever firstDealer |
| Check and adjust the intake and exhaust valve clearances | every 1000 h | every 4 years | whichever firstDealer |
| Check the propeller shaft alignment and the engine mounts | every 1000 h | every 4 years | whichever first |
| Inspect the wiring harness, connectors and the starter motor | every 1000 h | every 4 years | whichever firstDealer |
Free in Voydar Helm: each interval becomes a maintenance task, due by hours or by date, whichever comes first.
Source
Yanmar 4JH45 operation manual, periodic maintenance chapter, as summarised by secondary sources
Read from summaries of the maker's manual, not the manual itself.
Revision read: Secondary summaries (sbmarinemechanic.com, travelsketchsailing.com), read 2026-10-12; the maker’s manual was not consulted. Confirm every interval against the current Yanmar manual for your serial number.
Reference only. Intervals vary by serial number, use and climate; your engine's current manual and your dealer are the authority. Part numbers and diagrams are in the manual.