Same frames as I have - Caldwell's I believe. My boats previous owner had also added silicone in the corners, but water drains out from there, not in. I took the manky looking silicone out and my portholes don't leak.
Where I have had small leaks on a frame, Captain Tolly's and a strip of electrical insulation tape does the job til the weather is ok. I then took the frame out and replaced the old boatbuilder's gobber with closed cell foam strip as often recommend and additionally used a mastic bead to seal any gap left between the frame and the paintwork. A few years later, when that leaked again, I used automotive butyl rubber strip. Job done.
(If you use butyl, don't think it needs to be warm to stretch, compress or stick, cos it goes claggy and gets more difficult to do a decent job - if anything it's better to apply a bit cold.)