Most diesel engines are hearty creatures, so long as they receive proper maintenance. This is especially true when laying up for winter and fitting out in the spring. To make sure that you address all the details, here's a maintenance guide to keeping your diesel engine in top shape all year long.

SPRING COMMISSIONING

• Change the raw-water pump impeller(s).
• Check oil level and top off as necessary (if the oil was not changed at winterization, change the oil and filters).
• Clean battery terminals and apply non-conductive grease.
• Add water to batteries.
• Check all belts and hoses for wear, tighten belts to proper tension.
• Check that bolts and clams are properly tightened.
• When boat is launched and all of above are accomplished, start engine(s) and warm up.
• Check for cooling water flow through exhaust.
• Test engine overheating alarm.

BEFORE EVERY ENGINE START

• Check oil and engine coolant levels prior to start, and add fluid as necessary.
• Open raw water seacock (always leave this valve closed when the engine is not in use).
• Turn on battery switch.
• Run blower for five minutes.
• Start engine(s).

FOLLOWING EVERY ENGINE SHUTDOWN

• Before shut down, let engine(s) idle five minutes without load to properly cool down.
• After shut down, close raw-water seacock.
• Shut off battery switch.
• Check fuel levels in all tanks, and record in log.

MONTHLY DURING BOATING SEASON

• Check seawater strainer and clean as required.
• Back flush raw-water intake.
• Check fuel filter(s) and replace as necessary.
• Drain any water from fuel filter bowl.

EVERY 90 DAYS DURING SEASON:

• Check air filter(s) and clean if necessary
• Add water to batteries.
• Change oil and filter(s) if the engine has reached appropriate hours of operation (50 or 100 depending on manufacturer's instructions).

WINTERIZATION PROCEDURES

• Change oil and filter(s).
• Fill all fuel tanks completely full and add biocide and de-watering agents.
• Change the fuel filters(s).
• Clean battery terminals, and apply non-conductive grease.
• Add water to batteries.
• Check seawater strainer and clean as required.
• Flush the cooling system intake with fresh water.
• Exercise the raw-water seacock and leave it closed.
• In harsh winter climates, add antifreeze to the cooling system.
• If stored in water, visit the boat weekly to check for problems.
• If stored in water, start the engine(s) once a month for 30 minutes under load, or until full operating temperature is reached, to keep the oil up in the engine. Allow engine(s) to properly warm up and cool down.
• Whether stored on land or in water, consider marine-grade engine heaters unless your engine is equipped with block heaters.
• If stored ashore, charge batteries completely and then disconnect battery terminals. They will hold an adequate charge for up to three months. In the Spring, the evening before you plan to re-launch connect the battery charger overnight. If the boat is moored in the water, the monthly cycling of the engine should keep the batteries charged.