The cooking time for boiling a 750g gammon depends on the size and thickness of the meat, as well as personal preference for how well-cooked you like it. As a general guideline, a 750g gammon joint would require around 1 hour 15 minutes to 1 hour 30 minutes of boiling time.
To cook the gammon, place it in a large pot, cover it with water, and bring it to a boil. Reduce the heat to a gentle simmer, and let it cook for the recommended time. You can also add additional flavorings such as onions, bay leaves, or cloves to the water to add more taste to the meat.
It's important to check the internal temperature of the gammon before serving to ensure it has reached a safe temperature of at least 71°C (160°F). You can use a meat thermometer to check the temperature, or look for other signs of doneness such as the meat pulling away from the bone or the juices running clear.