You need a twin M-2 50 cal. mount on the bow.
All a question of weight placement. But not on the bow, because a sailboat is not a chaser, it is a “chase-ee.” Everything else is faster, so threats are coming up on the stern.
In my last novel (probably forever) “The Red Cliffs of Zerhoun,” the 60 foot steel trading schooner has an ex-Soviet-era 12.7mm “Dushka” on the stern. Like a cheaper version of the Ma Deuce M-2 fifty caliber.
On a sailboat, you just need to defend the stern. You can always turn the stern to the danger as the faster attacker approaches.
There’s no point to a gun on the bow. Everything else is faster than you are.
https://www.amazon.com/Red-Cliffs-Zerhoun-Matthew-Bracken/dp/0972831053/