Frequently Asked Questions

Over the years, we have received plenty of questions about diesel engine and propulsion systems.  We feel it may be helpful to include answers to some of the most frequent questions we are asked.  Most of these questions fall into the four categories below.   We're busy completing our list, so check back for more FAQs and Answers.  Diesel Engine Maintenance Recommended Spare Parts Transmission and Prop Questions Basic Troubleshooting

Diesel Engine Maintenance

Q:  How many hours do you recommend between oil changes?

A:  We believe that oil changes are a relatively inexpensive way to prolong the life of your diesel engine.  We recommend an oil change every 100 hours of engine time and at the end of every season before storage.

 

Q:  Do I really need to change my diesel engine filter with each oil change?.

A:  We recommend it!  Again, it is a relatively inexpensive way to prolong the life of your engine. If left unchanged, the filter keeps about a pint of dirty oil in your engine.  Its also busy doing its job, filtering out particles that you don't want circulating through your engine which means that it is slowly clogging up and decreasing the rate that oil is pumped through your system.

 

Q:   Should I be changing to synthetic oil for my marine diesel?

A:  There's no easy answer to that .  Synthetics hold great promise, but we suggest you see what the oil manufacturers are saying and what the engine manufacturers are recommending.  See our new page on synthetic oils for more information.

 

Q:   Should I use Original Equipment Manufactured (OEM) filters or aftermarket brands.

A:  OEM filters are frequently recommended by the manufacturer of your engine.  This is because they know that the part meets the specifications for the engine.  Aftermarket brands can also be a quality and, in many cases, less expensive or more readily available alternative.  Our advice is that you should use aftermarket brands ONLY if you know they meet your engine requirements. How do you know.  You can check with the manufacturer of your engine.  You can also look at available literature regarding the specifications of aftermarket filters--the internet is invaluable for this.  We know a great deal about both oil and fuel filters.  We stock popular versions of both.  If we don't know about your specific filter we will recommend the OEM and help you to to obtain the proper filter.

Recommended Spare Parts

Q:  I have a normally aspirated diesel engine.  What parts should I carry on my boat?

A:  That depends on a number of factors.  If you are venturing off-shore you will want a more extensive array of spare parts and maintenance items than if you do mostly day sails. 

• You definitely want a spare fuel filter because clogged filters are the number one cause of diesel engine stoppage in a boat.
• A spare impeller, gasket and tool to remove it would also be a "must have".   If your impeller stops pumping cooling sea water it is just a matter of minutes before your engine stops or you do severe damage to your engine, or both!  We like the SpeedSeal quick change impeller cover
• Next, a spare alternator belt along with any other belts that are necessary for your engine.
• Though not technically a part, an extra bottle of engine oil, transmission fluid, and spare diesel fuel is a good idea.

As you travel farther offshore you will need a larger collection of spares.  Additional parts might include

• A thermostat and gasket
• An alternator or voltage regulator
• An extra injector
• Primary lift pump (or install an electric auxiliary)
• Cooling and fuel hose replacements

We don't want to exhaustively list every item, but these are what we consider to be priorities.

Transmission and Prop Questions

Q:   How frequently should I change my transmission fluid?

A:   As a rule of thumb we suggest every 250 hours of engine time.  If you have a line wrap around your prop or have another event that puts an ideal strain on your transmission, we suggest you change the fluid. 

 

At other times, when you are checking your fluid level, look at the fluid.  It shout be clear with a slight pink tint.  If it is not, change it.  Smell the fluid.  If it has a burnt smell, change it.  Transmissions have very little fluid capacity and transmission fluids are relatively inexpensive.  Bottom line, fluid change is good maintenance and cheap insurance.

 

 

Basic Troubleshooting

Q:  I'm motoring along.  My engine begins to loose rpm's and then suddenly sputters and stops.  What should II check first?

A:   First, as the problem begins to happen, check your engine gauges, especially oil pressure and temperature. If you have a vacuum/suction gauge on your primary fuel filter, check that.  

 

If oil pressure is low, look for signs of a leak and add more oil.  If temp is high, check your raw water strainer and look for exhaust output, then, when the engine has cooled, place a protective rag over the fresh water (anti-freeze) cap and CAREFULLY open it to see if the level is low.  If your water pump is driven by a belt, check for slippage.

 

If the gauges seem normal, don't forget to quickly look around to see if you have a line in the water that has wrapped around your prop (usually resulting in a more sudden stoppage) or check for other obvious problems..like that fish pot that is suddenly following your boat.

 

95% plus of sudden diesel engine stalls are the result of failure in the fuel supply to the engine.  Accordingly..

• Check to make sure your fuel supply cut-off valve is fully in the ON position.
• Check to make sure you are not out of fuel!  We were actually aboard a sea-trial when the owners engine sputtered and died.  Looked like a fuel outage, but he assured us he had fully filled his tanks before storing his boat for the winter and there were no signs of leakage.  Turned out that he had also ordered a pump-out of his holding tank and the operator had mistakenly pumped out his diesel tank!  Really!!!
• Check your separator/primary to see if it is clogged and check or replace your secondary then prime and attempt to restart your engine.
• Loosen the nut to each injector, one nut at a time and prime until there are no air bubbles.

 

Check for other conditions.  If you have your engine manual aboard (recommended) check its trouble shooting list.

 

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