Now the Blue Sea 187 (which is a heavy duty circuit breaker which has a relatively "slow blow" curve) is certainly the series and quality that I'd use.

The wire capacity, per say isn't really necessarily going to simply protect you. If you use the Blue Sea web site's wire sizing function, you'll see that their recommendations relates not only to the amperage and wire length -- but also the voltage loss, whether the load is variable or constant (windlass would be "variable"), time of loading, etc.

If you take the 5 or 10% voltage loss limit and ended-up with a 4-0 battery cable; and, then loading that with 80 amps for a long-enough time would burn-down the boat by causing a fire. That would be well before the breaker would "trip".

On the other hand, if you under size the breaker, then the windlass will not serve you.

If you look at the data and you'll see that the issue isn't only the absolute breaker load, it really relates to the curve of the loading. You can see the momentary loading, then the sustained loading before a "trip".