1. **Oil and Filter Changes**
– Regular oil changes are critical to keep an inboard engine running smoothly. Oil lubricates the moving parts and reduces friction, preventing excessive wear. The oil filter should also be changed to remove impurities and ensure clean oil circulation. It’s generally recommended to change the oil and filter after every 50 to 100 hours of operation, or at least once a year.

2. **Coolant System Maintenance**
– Inboard engines typically use a closed-loop cooling system, which circulates coolant through the engine to prevent overheating. Over time, the coolant can become contaminated or depleted, so it’s essential to check coolant levels regularly and top up as needed. The heat exchangers and raw water pump should also be inspected for signs of corrosion or blockage.

3. **Fuel System Inspection**
– Inboard engines rely on clean, efficient fuel delivery for optimal performance. The fuel filters should be checked and replaced if clogged, and the fuel lines should be inspected for leaks or cracks. Modern engines may also have fuel injectors that need periodic cleaning to prevent buildup that could affect performance.

4. **Drive System Maintenance**
– Inboard engines connect to the propeller via a shaft or drive system. This system should be checked for alignment and wear. In shaft-driven systems, the shaft bearings and seals need regular inspection to prevent water from entering the engine compartment. In stern-drive systems (where the drive is mounted at the stern of the boat), the bellows and gimbal bearing require regular checks to prevent water intrusion and damage.

5. **Exhaust System Checks**
– Inboard engines have complex exhaust systems that require regular inspection to ensure they are functioning properly. The exhaust manifolds, risers, and hoses should be checked for leaks, corrosion, or blockages, as any malfunction could result in carbon monoxide buildup in the boat or water entering the engine.

6. **Transmission and Gearbox Service**
– The transmission and gearbox are crucial components that transfer power from the engine to the propeller. Transmission fluid should be changed regularly, and the gearbox should be inspected for signs of wear or leakage. Misalignment or worn gears can lead to decreased performance or failure, requiring costly repairs.

7. **Belt and Hose Inspection**
– The belts that drive accessories like the alternator, water pump, and air conditioning system should be inspected for wear and proper tension. Worn or loose belts can slip or break, leading to engine overheating or loss of power to critical systems. Hoses should be checked for leaks or cracks, particularly in the cooling system.

8. **Battery and Electrical System Maintenance**
– Inboard engines rely on a battery for starting and powering onboard electronics. The battery should be checked regularly to ensure it holds a charge, and terminals should be cleaned to prevent corrosion. The alternator, starter motor, and wiring should be inspected for proper operation, as electrical problems are a common source of engine trouble.