No it is not. I did a fight with Hachi (trinc) vs me (Santi). He was able to tag me from any position he wanted. So ofc i head no weather gauge. Ofc The way to succes depends on the captains you are facing but the rule of thumb is:
Gain weather gauge at all cost
Use Chain (its much more effective especially when no time to mast snipe)
get some space between you and the enemy
now either outrun and sail away (leave battle) or keep weather gauge and pound his hull from distance.
The biggest mistake you do is by getting cocky and try to hunt him down (going close) when the enemy is low on health especially when you give up weather gauge. That really can flip the tide of the battle.