[Stumble]

You may need to replace the sheaves since wire has a different groove profile than rope, and old wire sheaves are often damaged.

In terns of strength, a 3/16 amsteel halyard will be at least as strong as the wire you are replacing, but may be difficult on the hands. You can splice an amsteel length onto a larger end piece for handeling (texen or sta-set are common choices).

If you want to go all the way to 1/2" you also will need to look at replacing all of your deck hardware. Must small boat stuff won't be sized appropriately to handle line this size.

 

[Stumble]

Midnight,

Any wire sheave that is smooth can handle dyneema. But you would need to do a rope to rope splice instead of the rope to wire.

Frankly I can't stand wire halyards since I have too many scars from where I have been punctured. But whatever works for you.

 

[Stumble]

Dyneema is a relatively new line to the market (about 10years ago) that will be stronger and have less stretch than the wire you have now. Is pretty resistant to UV damage, and because you can size for size replace running rigging wire with it does not require replacing un damaged wire sheaves (damaged ones are another story).

For all intents and purposes there is no reason to ever use wire as running rigging anymore.