MONEY is being sought to replace two marine launches, one built more than 50 years ago, which are used as navigation aids. Legislators will be asked this month to approve $18.5 million for two new launches with up-to-date navigation equipment. In a paper to members, the administration said the existing launches were slow and not equipped with radar, making them unsuitable for use in remote locations, bad weather or poor visibility. One launch, used to help navigators inshore, was built in 1940 and the other, used offshore, in 1973. The replacement launches will be capable of higher speeds and will be equipped with facilities such as radar. One will have anti-pollution equipment. The Director of Marine, Allan Pyrke, had considered hiring launches instead, but he had found none which would be available without extensive modifications. It was expected that the construction of the launches would start in April and be completed in mid-1996. There are 341 aids to navigation in Hong Kong waters, consisting of fixed beacons and lighted buoys. Ship's officers use them to determine their vessel's position.