Quick question about catching the train in Napoli

Not risky at all. There is a tram from the port that will take you to the station. I don't remember the time but it seemed relatively short - maybe 15 mins. Certainly a taxi would be an option and quicker - maybe five minutes. It will take five minutes at the station to find your train.

BUT, this is a concern - weather. Weather can be bad enough to dispute the schedule or cancel the hydrofoil. So I would watch the weather forecast before making a decision.

Even in July weather can be bad enough to cause problems with hydrofoils? I'm a crazy planner and like booking things really early but I can wait to book until it gets a lot closer since now I at least know the timing should work

Do you really save anything by booking 4 months out? Do the ferries ever really fill up entirely? My advice would be to wait, even up to the day before or the morning of. If the weather looks iffy, take the early ferry, you really would not to walk around in the rain, do a nice lunch in Naples (hey, Pizza!), if it looks great, then enjoy a few more hours on Ischia. No need to plan out to the minute.

.....Even in July weather can be bad enough to cause problems with hydrofoils?.... Of course - thunderstorms are very prevalent in the summer and especially in the afternoon. And storms move from sea on to land in the summer. And even if the storm is not close it can create waves that can become a problem. So it is not a given that the weather is always calm. You probably will not have a problem but it is a possibility. Of all the things that can go wrong that would be first on my list. Getting to the train in an hour and five minutes would be very low on my list. The weak link in your plans is the hydrofoil.

And if you have purchased a discount ticket on line and miss the train it is a dead ticket. This might be a situation where buying a ticket at the station might be the best bet. How critical is your arrival in Rome?

I don't think you need to purchase your boat tkts in advance. We took a boat from Naples to Sorrento a few years ago and just bought our tkts maybe an hr before the boat left. Then went to a little outdoor cafe nearby and had a glass of wine while we waited. And yes, the weather in the summer can cause rough waters and delayed and cancelled boats. I will never forget a visit to the Cinque Terre in July 2009. We arrived in Vernazza mid-afternoon (sunny, warm, beautiful) and the tiny square was packed full of boats for safekeeping as the waves were coming over the breakfront, which was roped off to keep people from walking out there and potentially being washed out to sea! The waves were that incredible! Had been here twice before in the months of June and July and never experienced anything like this! It was quite something to see and the boats did not run the next day as waters were still rough. Please do a trip report on your thoughts on visiting Ischia. We had thought about a daytrip here from Sorrento last Oct. but the boats were not running that late in the season. Have a great trip!

The bus from the port to Napoli Centrale is called the Alibus. The stop is right outside the port. It runs every 30 minutes, cost is 4-5€.