The Battleship USS Missouri passes Honolulu en route to Pearl Harbor, Hawaii, where it would to become a museum near the Arizona memorial. The USS Iowa recently opened up as a museum in San Pedro, Calif. - 

Jeremy Hobson: Another big warship, the USS Iowa, has opened for tourists in San Pedro, Calif. It's one of dozens of decommissioned ships that operate as museums around the country.

But it's not always easy to keep the tourists coming, as Marketplace's Adriene Hill reports.

Adriene Hill: The lines outside the USS Iowa were long on opening day, and Robert Kent was clearly pleased.

Robert Kent: Good morning, good morning. Welcome to the Iowa.

He's head of the nonprofit that runs the new battleship museum.

Kent: Everything is A-OK right now. We're just so excited.

And it's a ship with history that visitors seemed pretty into:

Guide: This is where Churchill and Stalin and Roosevelt sat at that table there and discussed about D-Day.

The USS Iowa also has the only bathtub ever installed by the navy on a battleship.

But good history and a surprising tub -- it was installed for Roosevelt -- don't guarantee the USS Iowa will be a success. Some ship museums struggle. Others, like the aircraft carrier Midway in San Diego, thrive.

Turns out ships need a business plan.

Scott McGaugh: As noble as the mission is of preserving a particular ship, and its legacy and its contribution to our history, at the end of the day it's got to be a successful business.

Scott McGaugh is the marketing director for the Midway. For one, he says, you've gotta know your customer.

McGaugh: We've always been focused on the family, on the moms in the family and the kids, not just the History Channel buffs, if you will.

Location matters. New York, home of the USS Intrepid, is good. Camden, home of the USS New Jersey, is not so good.

And a ship needs a marketing plan. Jeffery Nilsson heads the Historic Naval Ships Association. He says opening a battleship isn't that different from opening a restaurant.

Jeffrey Nilsson: It could be the finest restaurant on the planet, and if it's not marketed properly, if it doesn't attract people, if it doesn't get people in the door, what's the purpose?

Snagging visitors helps keep a ship above water financially, but also just above water. The USS Texas, near Houston, had to close to the public because of leaks. It has since reopened, but supporters say a permanent fix could cost tens of millions of dollars.

I'm Adriene Hill for Marketplace.

Follow Adriene Hill at @adrienehill