Thanks!
Furuno makes very good equipment. However propagation conditions vary
by time of day in the shortwave bands because of changes in the
ionosphere caused by the sun. Typically, lower frequencies are
better at night, and higher frequencies during the day.
As an example I monitor the weather FAX out of New Orleans for
conditions in the Gulf of Mexico and the Caribbean. During the day
the best frequency is usually 8502 KHz and at night 4316 KHz.
The worldwide listing of weather FAX stations, frequencies and
schedules can be found here:
http://www.nws.noaa.gov/om/marine/rfax.pdf
The high seas voice forecasts follow the FAX transmissions: