Part II: Leaking Porthole and Portlight fixes that REALLY work!

Supplies:

3-5 sunny days in a row!
Putty knife
Acetone
Plastic shims
Masking tape
3M Marine Adhesive Sealant 5200

Step 1: Remove window.
Break the exterior window seal (ie. old caulk, sealant, gasket, etc.) with metal or plastic putty knife/scraper. Careful with a metal scaper as it can scatch the fiberglass. I ended up with a few scatches but they easily buffed out. Remove screws from galley side of window casing. From the interior, tap window frame with rubber mallet to loosen the seal.

Step 2: Remove old caulk.
Remove all old caulk or sealant from all surfaces, including window and boat hull.
Start with metal or plastic putty knife to get the bulk off and then continue with acetone or other paint thinner.

Step 3: Inspect.
Inspect all surfaces: wood core of boat hull (between the interior and exterior fiberglass layers) for water damage. If not already done, epoxy over any exposed areas. If water damage is found, please address appropriately. Good advice in general but my Coronado 25 is just fiberglass no wood core so I could skip this.

Step 4: Apply generous amount of caulking to window frame.
Insert window frame into the hole in the boat. Place the ¼ inch or smaller shims around the exterior edge of the window frame, between the frame and the hull. I used wood shims on the first window and one broke off with bits of it stuck in the caulk. Plastic worked much better. Tighten down window onto shims making sure there is a gap. The caulk will naturally squeeze out around the edge, but this is good because it creates a new seal. Wipe excess with rag. LET SET for 2 days.

Step 5: Remove shims.
Remove shims and tighten down the screws completely. Allow to SET for 5-7 days.