Med,
Having a 1980 Catalina, I am always finding new leaks that pop up. The boat flexes, caulks breakdown & deck wood shrinks etc.
When I find a leak, I scope & mark the area directly above on topside. From this center point of where the leak is visible below, draw a mental circle to include any higher thru deck fixtures looking at hardware and caulked seems. Water runs high to low, so your suspects are higher points first.
I cut the fiberglass area around my mast base to repair the mast step. What I found was hap-hazard balsa wood pieced together with seams running in all directions. Think of a loose fitting puzzle. Apex touched on this, but keep what he said in mind.
So,
#1 identify, all high points.
#2 for your water check, use either Apex or Higg's advice or both.
#3 another thing you might try is to get some good tape or easy to clean up cheap water based caulk & do all the high to low thru deck fittings. As apex has said, water can flow horizontally, so make sure you start out at all high to low fittings in order.
Start the water at the highest point and work you way down as you remove the temp. tape or caulk one fitting at a time. This has worked for me.
CR