Peter Hendra wrote:
Hi,
I am contemplating running a light wire back to the cockpit to operate the
anchor winch from there. At present the power is switched for up and down from
foot switches at the bow.

What is best - solenoids or relays? What is the difference please?

Solenoids are discerned as being heavier built than relays, but in
essence it's the same technology, where an electromagnet moves a
linkage for switch contacts. The word solenoid is more likely to be
used in a mechanical situation, perhaps where you might want a valve
actuated, or a heavy electrical contactor. A solenoid is usually
considered to be a single pole, single throw switch relay, or a
single off on function, like your starter motor solenoid.

The word relay usually connotes a more complex, lighter duty job,
with several independant circuits actuated, like reversing a motor.
This could also be done by switching transistors.

A remote control for a windlass requires a double pole double throw
set of contacts, essentially four solenoids with a total of eight
contacts, to reverse the motor in the windlass. Or, a large
mechanical dpdt switch could be used to reverse, with only a single
solenoid needed to turn the motor on and off. There is no need to
place the control circuitry close to the windlass, unless you have a
battery near the windlass to reduce wiring required, or want a local
hand or foot switch, too. The weight trade off is pretty moot, as is
the cost of wires vs. controls and a dedicated battery foreward.

It gets fancier if you want to be able to reverse the thing from
more than one location. A wired or wireless remote using radio is a
possibility, with all but the local foot switch operated by
electronics. When you are on the bow, a mechanical switch could
still reverse the active circuit, even if the remote reverser was
actuated, but then the mechanical switch could exhibit a reversal of
it's directions. A mechanical foot switch on deck would need to be
left in an on position if the remote was to be able to work, or even
more heavy wiring could be required.

A transistor bridging switch (heavy electronic relay) could be built
but I don't know if there is enough history to demonstrate their
ruggedness in this particularily onerous consumer marine
application, nor am I familiar with suppliers or use of such. In an
emergency, I would prefer a heavy mechanical switch hard wired so
the death of a transistor or a wireless battery could not make your
windlass useless.

Dialects being what they are, compounded by trade jargon, your
verbiage may vary. (YVMV)

Terry K