Exhaust Systems; Governor Settings - Hamilton Jet HJ212 Installation And Service Manual

Installation and Service Manual

Exhaust systems

Engine exhausts should not be located below the waterline near the jet units.
Engine exhausts should be sited above the waterline.
Water containing exhaust gasses can enter the jet unit when moving astern causing loss of thrust and
control.
The exhaust system can be any conventional system approved by the engine manufacturer.
1 Exhaust outlets
2 Exhaust gasses
3 Water flow

Governor settings

The no load governor setting (or high idle) on diesel engines, should be set well clear of the full throttle RPM
achieved when driving the jet unit so that there is no chance of the governor reducing power (and
performance) at full throttle. To check, select neutral and open the throttle fully. Measure RPM, using a
calibrated hand tachometer.
If no gearbox is fitted then disconnect the driveline at the engine flywheel and check RPM.
Example:
If the maximum RPM for driving the jet unit is 2800rpm, then the governor should not begin to operate until
at least 2850rpm. On most diesel engines this means the "no load" governor setting (or "high idle") should be
at least 3050rpm (i.e. 250rpm higher than the loaded maximum RPM).
Ensure that the low idle RPM is set high enough to avoid any vibration in the driveline. Extensive idling with
the driveline vibrating may damage the jet unit.
Figure 10: Exhaust System Layout
4 Chine
5 Keel
3-11
Design Basics