The Navy generally uses the spring-loaded flyball-type mechanical governors. All flyball-type mechanical governors have speed droop. This means, as the load is increased at a constant throttle setting, the In the idling speed range, control is effected by centrifugal force on the two sets of large and small flyweights, as shown in figure 4-1. This flyweight force acts against a light (low-speed) spring. Maximum speed speed of the engine will drop or droop slightly, rather than remain constant. Consequently, mechanical governors of this type are never used where absolute constant speeds are necessary.

Besides the spring-loaded flyball-type governors, there are several other types of mechanical governors. The two most common types are used on GM 71 engines. One type, the constant-speed governor, is used on generator sets and is designed to hold the speed of the engine at a predetermined operating speed. The other type, similar in construction, is used primarily for propulsion engines. It has a throttle plate designed so that intermediate speeds may be obtained by manual adjustment. Notice that there is no buffer spring adjustment on the constant-speed governor. The following description applies to both types of governors.

Figure 4-1.GM mechanical governor.

control is effected by the action of the high-speed (small) flyweights acting against a heavy (high-speed) spring. See figure 4-2. If you have any questions or need more illustrations to understand the concept of governor operations, refer to chapter 9 of Engineman 3, NAVEDTRA 10539.

Mechanical governor faults are usually revealed in speed variations. But not all speed variations are faults of the governor. When abnormal speed variations appear, you should first do the following procedures:

1.Check the load to be sure the speed changes are not the result of load fluctuations.

2. If the load is steady, check the engine to make sure all the cylinders are firing properly.

3. Make sure there is no binding in the governor

mechanism or operating linkage between the governor and the engine. There should be no binding in the injector control rack shaft or its mounting brackets. If you find no binding anywhere and the governor still fails

Figure 4-2.Mechanical governor control mechanism.

to control the engine properly, you may assume that the governor is worn or inoperative.

If the governor is the cause of improper speed variations, it must be completely disassembled, inspected, and rebuilt or replaced. When it is necessary to disassemble and reassemble the governor, you should secure a copy of the manufacturers instruction book and follow the instructions given. During reassembly of the governor, use only hard grease on the gasket! Under NO circumstances should you use shellac on the gasket. Adjustment procedures for the replacement of any governor are listed in the manufacturers instruction manual and should be followed with particular attention given to the precautions listed.