Starter Motor Maintenance

Preventive maintenance and starter motor maintenance is essential to ensuring reliability. A common problem especially on little used vessels is the formation of surface corrosion, or accumulations of dirt on the shaft and pinion gear assembly, and lack of operation and lubrication causes seizure or a failure to engage.

It is good practice to operate the starter as often as possible, the heat dries the windings out and also remove the starter every 12-18 months or prior to an extended cruise to clean and lightly oil the components according to manufacturers recommendations. Alternatively drop the starter into your local automotive electrician who can run a quick test and perform the basic maintenance.

Starter Motor Maintenance

The most common problems occur with seized brushes, and this is due primarily to a lack of use. Where the starter design allows access, manually check that brushes are moving freely in the brush-holders, and that the commutator is also clean. Remove all dust and particles using a vacuum cleaner.

If the commutator is dirty wash it and the brush gear out with a quality spray electrical cleaner if badly soiled. Under no circumstances clean and polish the commutator with any abrasive materials as this will quickly ruin it. Commutators build up a surface patina that should not be removed, as sparking brushes will rapidly degrade the surface and edges of the slots.

Starter Motor Maintenance


There are few of us who haven't heard the deafening silence of that ominous click, and a failure to start, or a chattering solenoid or a failure to get the diesel turning over fast enough to start. The following are typical faults to look at when troubleshooting.

Starter Motor Maintenance


Low Voltage is the most common cause, and the battery and battery connections are the first place to look. The main starter motor and solenoid terminals are the next common failure area and often work loose or make inadequate contact. Warm or hot terminals are a good sign of problems and I have seen smoke curling up on some occasions from battery and starter connections. Also check the engine negative connection, as loose bolts are common. That is caused by a lack of starter motor maintenance.


Winding overheating on marine engine starter motors is a direct result of attempting too many starts or excessively long start attempts. The marine engine cannot be turned over at the required speed either due to lower voltages, or excessive loads especially in cold conditions where high oil viscosity is a factor. Partial or complete failure of the preheating glow plugs is also a reason for slow starts and this should be looked at.


Excessive starter motor noise and vibration may indicate that bolts are loose. Bearing failures are comparatively few in marine-engine boat starters as the number of starts is relatively few. Another cause of noise can be attributable to the pinion drive and the overrunning clutch having defects or jamming when disengaging.


Without the starter the marine diesel engine is just another piece of cold iron or an anchor. Starter reliability and performance comes down to ensuring the cables and power supply are sound, and the connections secure. In addition the minimization of seawater exposure and maximization of starts will reduce increase reliability and reduce failures. All these tasks are within the scope of any boat owner, and only require simple vigilance and routine visual tasks.

Make starter motor inspection and starter motor maintenance an essential part of your boat maintenance regime, it will pay off.

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