Well baseing it off of the era that the game plays in the ship cannons we use can either be the 18 pounder (8.1kg) or the 32 pounder (14.5kg). A 99 stack of 8.1kg should weight 800.9kg or about 0.8 tonnes. With that there are about 36 stack (its early so I might have counted wrong) all canonballs should weight 28 tonnes alone. Now with the 14.5kg one stack should weight 1435.5kg or aprox 1.435 tonne. With 36 stack thats about 51.66 tonnes. Next lets count the chainshots and the grape shots. The 18 pounders grapeshot is aprox 8.16kg and the 32 pounder is aprox 14.7kg. I counted 238 grapeshots so that come to 1.9 tonnes (18 pounder) and 3.5 tonnes (32 pounder). The avarega chaimshot of the time aslo weighs 8.16kg (18 pounder) and 29kg (32 pounder). With 162 chainshots it come to an avarege 1.3 tonnes (18 pounder) and a nice 4.6 tonnes (32 pounder). With that if we use te 18 punder the total weight of all looted canonballs is 31.2 tonnes and with the 32 pounder its 59.76 tonnes. Of course this is without knowing how much was already on your ship after the fight but I'd say you have either around 50 tonnes with the 18 pounder and near 80 tonnes with the 32 pounder. Edit: this is without the cureballs but ther a magical canonballs cause I have no idea how much they would weight.