First of all, Spike Power is NOT the same as Firepower. Spike Power means: the maximum amount of Damage you can deal with one (1) broadside. Spike Power is important if you want to sink other ships quickly. Heavier cannons have more Spike Power, but take longer te reload. See Damage-Per-Second for more information.
To increase your Spike Power, you can use Fittings, Skills and Gunpowders that either give Damage or Accuracy.
For more information, look at the table below*.
| Cannon | Damage* |
|---|---|
| 4lb | 24.0 |
| 6lb | 26.0 |
| 8lb | 28.0 |
| 9lb | 30.0 |
| 12lb | 33.0 |
| 16lb | 36.0 |
| 18lb | 39.0 |
| 24lb | 46.0 |
| 32lb | 54.0 |
| 42lb | 63.0 |
*Do note that the listened Damage (in the stats) is NOT the actual damage you deal. Their are alot of factors which either increase or decrease damage output. For more information, click here.
This information is provided by the update that PotBS Wikia is undergoing, by Captain Vuur.