FAQ Marine Diesel Engines

Your yacht’s engines should be serviced at least once a year or every 100 – 200 hours of operation. Always refer to the manufacturer’s guidelines and consult with a professional technician at SB Marine mechanic.  Marine Diesel engine maintenance schedule to help with determining when’s best for your maintenance appointment. Hourly service intervals include 200, all the way up to 4,000 and beyond.

No, you do not have to be present. We are completely mobile and can meet you anywhere whether at your home, boat yard or harbor.    The majority of our communication is via phone and email. Clients who provide flexible access to their vessel, such as combo or key location, are processed in a timelier fashion.

From annual mechanical maintenance to the most complex in-frame Diesel engine rebuilds, re-powering and generator upgrades, our team of professionals will be there to assist you with your application, repair, service, maintenance, or purchase and installation.

Many people aren’t sure whether they should rebuild, repower, or overhaul their engine. Our marine diesel mechanics in Santa Barbara may suggest repowering your engine if it is a 2-stroke engine with high fuel usage, or if it’s an older engine in an area with lower air quality. Otherwise, you may consider an overhaul.

We regularly perform pre-purchase engine surveys. This consists of an in-depth visual inspection coupled with extensive computerized dealer level diagnostic testing. sea-trial data recording. engine & transmission oil analysis. cylinder compression test. cooling system pressure test & borescope testing available. We then provide a detailed report with any deficiencies noted. pictures of the deficiencies and an estimated cost to repair. This is crucial to assess the current state of the high-performance engines, gearboxes and generators in your new vessel.

Marine diesel engines emitting smoke can be a sign of underlying issues. The color of the smoke provides clues about the nature of the problem. Let’s break it down.

Blue Smoke:

usually indicates burning oil within the engine’s combustion chambers. possible reasons are. worn valve seals and piston rings, overfilled crankcase, blocked crankcase breather system. these are some of the usual culprits.

Black Smoke: 

Black smoke results from excess, partially combusted fuel or inadequate air supply. Possible reasons.

• Dirty, worn, or malfunctioning injectors
• Incorrect timing
• Over-fueling
• Faulty turbocharger
• Incorrect valve clearance
• Incorrect air/fuel ratio
• Low cylinder compression
• Dirty air cleaner
• Restricted induction system
• Carbon in intake manifolds
• Incorrect engine tune
• Poor quality fuel
• Excessive carbon builds up in the combustion chamber
• Cool operating temperatures

White Smoke:

white smoke in a marine diesel engine can be caused by several factors.

At start-up, the marine engine is cold, and it is normal to see white smoke appear. Indeed, at low pressure when the engine is idling, water vapor is formed. The white smoke that comes out of the marine diesel engine is produced by this water vapor. However, this should go away on a healthy engine once it is warmed up to running temperature. if white smoke persists these are a few of the culprits.

• Poor Fuel Quality (Low Cetane Rating):
• Low Inlet Air Temperature:
• Low Coolant Temperature:
• Low Compression Ratio:
• Incorrect/Failed Fuel Injection Components:

A Yacht Sea Trial is basically a test drive for a boat. It provides prospective buyers with the opportunity to observe the boat in action, try out its equipment and instruments, and get a feel for its maneuverability at different speeds—both underway and at the docks. During a sea trial, several important aspects are assessed:

We suggest following the engine manufacturer’s recommendation. It is recommended that you change the coolant in your marine diesel engine’s cooling system approximately every 2 years. Even though the coolant will still cool the engine, the corrosion inhibitor substance within the coolant tends to deplete over time.

most marine diesel engine manufacturers typically recommend an oil change every 50 – 100 hours, or yearly. Even if your engine manual allows for a longer interval between oil changes, changing the oil more often will extend the life of the engine.

• Insufficient motor oil
• Engine oil contamination
• Clogged oil filter
• Low or high viscosity
• Engine wear
• Sensory issues, meaning that the oil is fine, but the oil gauge is malfunctioning.
• Engine Speed: The oil pressure tends to increase with higher engine speeds due to the increased demand for lubrication. However, excessively high oil pressure can also be a sign of underlying issues.
• Engine Load: Heavy loads or towing can put additional stress on the engine, resulting in increased oil pressure requirements. It is crucial to monitor and maintain proper oil pressure to ensure optimal engine performance under varying load conditions.
• Oil Viscosity: The viscosity of the engine oil affects its ability to flow and maintain proper lubrication. Different engine designs and operating conditions may require oils with varying viscosity ratings to maintain the ideal oil pressure.
• Oil Temperature: Oil temperature plays a significant role in determining the oil pressure. As the oil heats up, its viscosity decreases, leading to lower oil pressure. Conversely, cold temperatures can increase oil viscosity, leading to higher oil pressure. It is important to monitor and maintain the oil temperature within the recommended range.

Fuel filters are typically ready to be changed every 200-300 running hours or once a year. If the fuel quality is suspicious or if you are seeing more debris in the primary filters than normal, you should change the fuel filters at half the normal interval above. if the engines are losing power or if there is a fuel system related alarm accompanying poor performance.

The filter element may be 2, 10 or 30 microns, indicating the size of the particles it will catch. A 2-micron filter element is reserved for secondary filtration, downstream from the primary filter. Both 10- and 30-micron filters are installed between the engine and fuel tank. Check with your engine manufacturer for recommended size to ensure the proper fuel-flow rate. Marine Fuel Filtration “The Seaboard Way” – Seaboard Marine (sbmar.com)

• blockage at the raw-water intakes and/or strainers.
• The next culprits are water pumps, their impellers, and supporting systems such as drive belts.
• There are plenty of other potential problems like scaled-up heat exchangers or clogged hoses.

• When your yacht’s engine won’t turn over, the first step is to ensure that the battery switches are turned on and the throttles are in neutral. Then verify that the batteries have juice. If they do, you more than likely have a bad solenoid or a bad starter.
• If the engine cranks fine but won’t start, the cause is probably either fuel or air related. That means the first step is checking and cleaning filters—any and all of them. If there aren’t any problems there, you could be dealing with contaminated fuel.
• If fuel system is cleaned and ruled out as a culprit. then there are numerus other causes for the problem.

Replacing zinc anodes in your marine diesel engine is essential for preventing galvanic corrosion. Most engine manufacturers recommend changing them yearly. The number of hours that you use the engine, and the salinity of the water will have an effect on the zinc corrosion rate.

Sea water impellers made of rubber wear out like all moving parts. According to most engine manufacturers, you must inspect the impeller yearly and/or replace the impeller yearly or after a predetermined number of operating hours.

• aftercooler/inner cooler clogged? the net result is a general loss of power and efficiency. This can occur because the thin metal fins grow dirty on the air side and/or have scaling on the water side.
• clogged fuel filters, clogged fuel lines and pick-ups, suction air leaks in the fuel supply, out of adjustment throttle linkage
• Dark smoke indicates overloading, not a fuel supply issue.
• dirty/clogged. air filter. Marine Diesel Engines use a mix of Diesel fuel oil and air to generate power. Air taken in from the outside goes through a filter to keep out dirt, debris, bugs and other contaminants. If the air filter has not been cleaned or replaced in a while, it will prevent the engine from generating enough power.
• these are a few of the possible symptoms but this list is long.