Looking at some of the previous versions of the Minotaur gives an idea of what probably won't work and what might (its had a few direct and indirect changes)
Initial release - Projectiles were much faster (800m/s compared to current 550m/s), armor damage was much lower (both per shot and over time), rate of fire was higher, knockback per shot was lower making knockback over time slightly lower overall, turning arcs were wider - 45 every way instead of 30. It was widely hated as OP because it could knock ships around and break components at considerable range (for reference at 800m/s its projectiles were faster than the mercury field gun at 750m/s).
It got nerfed heavily within a month - Speed dropped from 800m/s to 350m/s, shatter damage (gun and engine) dropped from 35 to 28. The reduced speed made it really hard to hit with because although other guns have a similar speed they have visible projectiles allowing gunners to correct their aim.
Heavy clip got nerfed - Minotaur lost even more of its long range capability, Hwacha got buffed to 'compensate' for the change meaning even less reason to use a Minotaur instead.
Minotaur got overall buffed but lost some things - Stats were changed to their current state, damage and knockback increased significantly, rate of fire decreased (not so much as to cancel out the buffs), turning arcs were reduced, shot scatter was increased and shot speed increased to the 550m/s middle ground. The loss of turning arcs killed my attempts at making Minotaur fish work since the side guns were now out of arc when the Minotaur was in, it also made it less useful as a defensive weapon on a galleon. Lochnagar became useful for long range sniping due to the increased damage and speed and its -100% scatter.
Lochnagar changed - Minotaur got 2 shots instead of 1 meaning it can do some serious damage but the scatter reduction went from -100% to -60% (the difference being between mostly hitting the ship and entirely hitting one of its guns)
My preferred option for balancing the Minotaur
-Reduce scatter from 3.5 degrees to somewhere around 2, this will increase its range, damage and knockback in practical effect
-Reduce knockback more than needed to compensate for the above, if the Minotaur becomes widely used while having a high knockback it will be hated, knockback should be a secondary effect
-Increase turning arcs back to 45 degrees so it can be used on goldfish again, increase turning speed somewhat to match