MJM Yachts 40z Express - Manual (Page 7)

CHAPTER 1
Compass Heading & Calibration
There are 3 heading references for navigation on the 40z: (1) The compass on the dash, (2)
Autopilot digital compass, and (3) GPS COG (Course Over Ground). All of these headings should
be within a degree or so of each other when underway. If not, it is recommended that differences
be recorded on a deviation card after following the calibration method outlined below or
better yet, employing the services of a compass adjuster. Use COG as the primary reference
at a time when you are not influenced by wind/wave/tidal set. The digital compass sensor is
located on a stringer outboard to starboard under the cabin sole. It is accessible by opening the
cabin sole hatch and looking aft.
Ritchie Ship’s Compass Calibration Method
1) With the compass in its intended position, but not finally secured, select a course on your chart
using two identifiable marks, buoys or landmarks that are within ten degrees (10°) of the
north/south line. Try to select this course so that you can maneuver your boat "down range" of
the marks selected.
2) From a position down range of the North/South marks, and keeping the marks lined up, run
the boat visually along the northerly course selected. Turn the port/starboard compensator on the
right side of the compass until the compass reads correctly.
3) Reversing direction, run the boat southerly, again keeping the marks lined up. If the compass
is not correct at this time, there is an alignment error. To correct, rotate the compass itself to
remove one half of this error. Repeat Steps 1 and 2 and then recheck this Step 3.
4) Simply repeat the procedures of Steps 1, 2 and 3, except this time, using an east/west course
and the fore/aft compensator on the aft side of the compass, although at this time any alignment
error should have been eliminated.
5) Upon completing the procedure, secure the compass in its final position.
Boat Speed Rather than a paddle wheel or sonic device, the Raymarine C120 plotter is used to
generate SOG (Speed Over Ground) that is displayed by the chart-plotter and may also be
shown in larger digits on the Autopilot display. Eventually, you will learn to approximate boat
speed through the water by relating it to RPM on the tachometer.
1.5
A facility that is unfamiliar with the 40z may require information before hauling the boat with a
Travelift or crane & straps. Refer to the illustration included at the back of this manual. The keel
(centerline of the boat) and chines (edges) should be used to position weight-bearing supports.
You will note that the fore and aft lift points are located approximately at either end of the
pilothouse... e.g. abeam of the windshield and the aft end of the hard top.
Point loading flat areas other than centerline and chine or setting the weight of
the hull on supports of insufficient area may result in damage to the hull.
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OPERATION
Avoid storing steel or iron items such as tools nearby.
HAULING OUT