That _seems_ like it should work.+1 on the taste test for boats living in salt water. Best method ever for finding deck leaks is to use a pressurised common garden sprayer and hit all the suspect looking areas on the deck one at a time from different angles. Don't be surprised when a found leak exits the boat at a totally different location to the source.
Get a roll of paper towels. Before you leave the boat for the week (or however long you leave it for) place or tape or whatever a paper towel at each location that you suspect might be leaking.
Next time you come back, it will be obvious whether the paper towel had gotten wet while you were away.
You may have to do this multiple times to track down the actual source of the leak, but it's the best method I know of for tracking down the mysterious ones that only leak when you're not around to see.
Leaks that only happen when you're not around are (in my experience) usually above the waterline and the result of rainwater getting in ... since most people who can choose when to sail don't visit their boats when it's rainy.