10 Important Generator Design and Operational Features Ship Engineers Must Know

Every time a ship engineer goes on board, he/she has to learn, understand and master the operations and maintenance procedures of the assigned machinery.

An engineer will come across a variety of generator types with different constructional and operational features during the course of his or her career on board. It is therefore important that the engineer knows the basics of a generator machinery system inside-out.

Below is a list of some not-so-commonly-known constructional features of marine generators and some overlooked but important generator procedures that are often not discussed or taught in training sessions or marine engineering books.

ship generators

1. Air start motor: Modern marine generators are provided with air start motor which supplies starting air to the combustion chamber. This motor will disengage once the generator RPM reaches approximately 70- 90 RPM depending upon the manufacturing features. In case of emergency or black out, a small switch or knob is provided on top of the motor to start the generator from local.

Air start motor

2. Oil filter cleaning feature: Marine generator is fitted with a duplex oil cleaning filters in the lube oil line. In some generators, these filters come with a quick cleaning feature that can be applied in case of emergency and when the lube oil pressure is low. The changeover handle of the filter is driven in to and fro motion multiple times, which causes cleaning effect on the filter and a sudden rise in the lube oil pressure.

3. Telescopic pipe: Telescopic pipe arrangement is common for supplying lube oil to the piston in two stroke main engine. Some generators (e.g. Daihatsu etc.) are provided with telescopic pipe connected in the piston for lubrication purpose. While overhauling the generator do not forget to remove the telescopic pipe prior to opening the piston.

4. Fuel pump block and floating shaft: This is one unique construction feature of generators like SKL where the fuel pumps are fitted in a separate block (fuel pump block) and connected to the generator by means of a floating shaft for operating the pumps.

5. Isolation rubber: Some generators with high power output have an arrangement of friction pad coupling to connect the prime mover shaft to the flywheel. No fitted bolts are used for this, instead the rubber pad friction holds the flywheel and prime mover shaft together.

Isolation rubber

6. Long term shutdown: When the generator needed to be shutdown for a long time (3 or more months) it is wise to use an anti-rust spray on the liner surface and other moving parts of the generator.

ship generator

7. Indicator cock: While taking up the performance of the generator, the indicator cock is opened. It is important to open all the indicator cocks in full open position. If the indicator cock is half or semi opened, the high velocity hot combustion mixture coming out of it will damage the valve and seat of the cock.

8. Cold Start: In cold condition, if the generator refuses to start in multiple attempts, open the indicator cock and turn the engine with turning gear with lube oil pump running. This will remove the accumulated fuel from the cylinder and avoid any explosion from blow back, which may damage the combustion chamber parts or even lead to accident.

9. Air manifold drain cock: In conditions where the chances of moisture accumulation are high, the air manifold drain cock should be opened up to 1/4th turn at all times even when the generator is running. This will ensure all the water collected due to moisture is drained and damage to the engine cylinders is prevented.

10. Injection Valve: Efficiency of the generator depends mainly on the condition of the injectors, which needs to be pressure tested and overhauled regularly. While replacing the nozzle of the injector, it is very important to loosen the pressure setting screw (located either on the top or on the side of the injector body) before opening the nozzle holding case nut, else it will damage the mating surface of needle, spacer and the straight pin.

It is to note that the above listed features are not present in every marine generator model. Do read the generator manual before performing any kind of maintenance or while operating the generator.

Related Reading:

10 Major Tests For Major Overhauling Of Ship’s Generator

10 Situations When Ship’s Generator Must Be Stopped Immediately 

10 Signs That Indicates Ship’s Auxiliary Engine Needs Overhauling

Over to you..

Do you know any other important point that can be added to this list?

Let’s know in the comments below.

About Author

An ardent sailor and a techie, Anish Wankhede has voyaged on a number of ships as a marine engineer officer. He loves multitasking, networking, and troubleshooting. He is the one behind the unique creativity and aesthetics at Marine Insight.


  1. I must thank who so ever has created this medium to encourage young engineers and career persons like me.you are really doing a great job please keep it up.let also use this medium to ask for an assistant from my senior in the marine industry, I am a young marine engineer searching placement onboard ,i will very grateful if you assist me with more information which will be very help to me as a marine engineer.

  2. The above article was very helpful thank you sir if can you write a article on the management of spares onboard it would be very helpful for junior engineers thank you

  3. U guys r indeed awesome, ur articles r very simple to understand n very easy to follow, really thumbs up guys do keep on posting very eager to read new more articles.
    Keep up the good work continuing?

  4. @ Yogi: It is because of our readers like you who keep motivating us to do better. Thanks for the appreciation.

  5. After routine maintenance on one of the cylinder heads on a V18 Hedemora diesel alternator, one of our engineers neglected to bar the engine over with the indicator clocks open.
    Instead he simply started the engine and made the ensuing situation worse by starting the engine remotely from the control room which was on another deck.
    Unfortunately the cylinder which he had been working on was full of cooling water due to a leaking seal which should have been replaced during overhaul.
    The damage caused by the ensuing hydrolock bent the crankshaft, piston rod and other associated parts. The crankcase was punctured also.
    The repair essentially was a new crankshaft, new engine casing and a full rebuild.

  6. After reading your article, I wanted to learn about marine engines and I came across one. It was helpful and easy to understand. Its about marine ratings, but I feel like the info that will be helpful to marine engineers.

  7. Firstly, please correct the word generator…. this may mean alternator in some industry usage.
    Its better to use the word generator engine to avoid confusion.

    Secondly, you may refer credible authors as a guide for your discussion ie, as in transactions of institute marine engineer UK or US coast guard or Hong Kong Polytechnic

    As senior lecturer of Sarawak Maritime Academy, please grade your discussions as to what level of knowledge ie CoC class 4 or higher level so as to enable your reader to know their expectation level of competence

    Lastly, I appreciate your effort but the contents of your discussions is quite superficial….. possibly for junior engineers may be it is of great assistance.

    I thank you.

  8. If possible, please address the issue of converting from ship’s electrician to ETO for high voltage vessel.

    This is good for potential shipboard candidates to enable them to carry on being relevant in their respective roles in the industry.

  9. Excellent write up on terms and definitions. I would have to agree that the use of “generator” word could be a bit confusing but thanks for the insight!

  10. Why platinum is use in oxygen analyser in wheatstone type and what is the working principal this instrument.

  11. The air start motor mentioned above will crank the engine by engaging the pinion with the flywheel. Once the rpm is reached it will get disengaged.

  12. Very informative discussion.Iwill really appreciate if someone can guide me if a Mak 6M20 (950) KW generator engine can be run on HFO ?If yes what extra arrangements are needed like fuel heating temperatures and nozzles pressure adjustments etc.

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