Regular oil changes are the single most important maintenance task for your marine engine. Understanding the right interval can mean the difference between an engine that lasts decades and one that fails prematurely.
Recommended Oil Change Intervals
The general rule: every 100 hours or annually, whichever comes first.
| Engine Type | Hours | Time |
|---|---|---|
| 4-Stroke Outboard | 100 hours | Annually |
| Inboard Gas | 100 hours | Annually |
| Inboard Diesel | 100-250 hours | Annually |
| Stern Drive | 100 hours | Annually |
For engine type differences, see Outboard vs. Inboard Maintenance.
Why Annual Changes Matter
Even with low hours, change oil annually because:
- Moisture accumulates in marine environments
- Combustion byproducts create acids
- Additives break down over 12 months
- Condensation occurs with temperature changes
⚠️ Important
Change oil before winter storage, not after. This removes acidic contaminants. See our Winterization Checklist.
Warning Signs
Watch for: dark/gritty oil, louder engine, decreased performance, dropping oil level, or warning lights. Multiple signs may indicate bigger issues—see 7 Signs You Need Professional Service.
For professional oil changes and engine service, find marine mechanics through Boatwork.
