[Suicide Junkie]

The top speed referenced in the ship hull is just the point at which normal engines stop having any effect (some sort of structural stress derived speed limit)

One of the key points is that the actual top speed (sum over "propulsion base" divided by "# engine slots") should have nothing to do with the engines.

So, even if your engines are completely destroyed, you'll still have a top speed of say 10,000.