We’ve been fitting mechanical (non-electric) Murphy gauges to our yachts for 30 years. In this era of electronic controls, and the NMEA 2000 backbone, why it this necessary?

First some comments on how these work. The three gauges in the lead photo are for transmission oil pressure, engine oil pressure, and engine temperature.

There are also Murphy gauges for engine coolant level (above) and oil level.

These have adjustable electrical contacts, so the user can determine the alarm value. For example, engine temperature might be set at 195F, oil pressure at 30 pounds, and transmission pressure at 250 pounds. These values are just outside of normal operating parameters. When the contacts close the signal is then used to trigger an alarm function.

So why go to the expense of fitting this gear?

• These gauges give an early warning of incipient problems, which can be easily changed with a small Allen key. As such, they are a major improvement on most engine alarms which only trigger when there are major problems.
• They provide a mechanical backup (therefore reliable) to electric sensors. If the electric oil pressure gauge drops is it because of a loss of oil pressure or a sensor or wiring problem? A glance at the Murphy gauge tells the story.
• When checking the engine room they provide immediate feedback.