Wire line is both heavier and thinner than mono or braid line, so it will come as no surprise that it sinks faster. Wire line intended for trolling is produced in one of two materials single-strand stainless steel or single-strand monel wire:~
Both stainless and monel are available in several breaking strains of between 15lb and 100lb and are normally sold in 50m spools, two of which may be connected.
Trolling with wire is best done at low speed, enabling maximum depths to be achieved.
As a general rule, when trolling at 3 to 4 knots, each 20m of monel line deployed will get your lure down about 2m, so 100m will achieve a trolling depth of around 10m.
Trolling with a greater length of wire than this tends to be counterproductive, as the cumulative drag causes the line to plane back up.
Used in conjunction with a deep-diving plug - like the Rapala X-Rap Magnum Divebait shown above - can add a further 30 feet (9m) of depth without the use of an inline trolling sinker. Incorporating a trolling weight will add an additional 5 feet (1.5m) for each 4oz of lead.
A rail mounted centrepin reel like an Alvey 'Reef Master' is a convenient way to fish with wire, but if you choose to use a rod, then the outfit needs to be optimised for wire:~
With the heavy outfit in particular you won't want to play the fish conventionally - the lack of stretch and the weight of the gear would be prohibitive. Leave the rod - ideally a bent-butt type - in the rod holder and simply winch the fish in whenever it's not taking line.
Use the Haywire Twist for connecting wire to a swivel, and the Albright Special Knot for connecting wire to mono or braid.
There's another method of making the connections in a wire trolling rig, and that's to use a swivel between the wire and the backing and another one between the wire and the leader.
If you're using an Alvey reel then any good quality barrel swivel will do the job. With a rod you'll clearly need swivels that can pass through the rod rings or negotiate the rollers without getting hung up - 'Aussie' type swivels with their narrow diameter and high strength are the ones to use here.
Wire line of any kind must be used with great care, as a trip to the cheese counter at your local supermarket will demonstrate. I always use a long mono leader so that when my catch is close to the boat all the wire is safely back on the reel.
This is a particularly good idea if you're using a trolling weight attached between the wire line and the leader, necessitating handlining the fish up to the gaff.
And of course if you expecting a wahoo to put in an appearance you'll need another shorter wire leader ahead of the lure.