Ofc. I can explain: It's too few heatsinks, because you are running only lasers (aka "Laserboat"). To maximize your damage you need to stack as many as virtually possible, i.e. in your case balance speed+heatsinks as good as you can. If you compare yourself with assault laserboats such as Stalker or Awesome, these run 20+ DHS with their (SRMs+) Lasers, e.g. STK-3F with 4 LL and 24 DHS or 3PPC-AWS with 22 DHS. So the 15 you were running are extremely meager causing you to frequently slow your rate of fire. It's not like 17, 18, 19 will completey nullify it, but it will guarantee you a higher DPS over time.
If you find yourself legged so frequently you can strip from the arms and rearrange to the legs. You probably lose lots of leg armor while jumping. You can also sack a JJ to maximize the armor, I just don't know what your habits/needs in your playstyle are (hence mine is just a suggestion).
Assaults only use the minimum heatsinks, when they use ballistics or LRMs, because these only generate comparatively small amounts of heat.
The only thing I can guarantee you, is that with higher front armor and more heatsinks your score will be higher. I don't think you will notice if you're running 96kph or 98kph. I would start with an engine rating that is a multiple of 25 and only as a last optimization step (and after many in-game tests) consider as a last resort a weird engine rating like 330 or 340.
Edited by Autobot9000, 05 September 2013 - 02:58 PM.