I am working through all the minor repair items on a new to me boat next on my list is transom LED removal and repair. At some point instead of fixing factory installed Shadow Caster transom LED's someone decided to stick another set of Blufin LED's on the transom which looks like shiite Shadow Casters are oblong Bluefins are large diameter round yes I have a bad case of OCD. I plan on pulling the Bluefins off and replacing the dead shadow casters. I will have 3 small 1/8" holes and 1 larger 1/4" hole when I remove the Bluefins my thoughts are to use Marine Tex epoxy putty and tint it black with the Marine Tex recommended tint.

Is this a bad idea or is there a better solution?

I would just make sure the hole is cleaned of any silicone that might have originally been used to seal them to the transom. Epoxy will seal it up nice. I’ve used it on mine and sanded it smooth,can’t even feel it with a fingernail after buffing the gel.

I'll never figure out the fascination with underwater transom lights in view of the potential for water penetration problems into the transom core down the road , but to each his own .

Do NOT use marine tex. Far too brittle and not resinous enough to penetrate the substrate materials and bond permanently no matter how nicely the end result may look . It will eventually break away , and in goes the water .
Drill the the existing holes a size or two larger and bevel (or countersink) the outer hole area and use a wettish epoxy resin filler that will bond well with the glass and inner wood. For little jobs like this I like to load the mixture in a small syringe and force it in the hole. It may be necessary to sand flush and re-paste again to get a nice even finish but it will bring you long term peace of mind.
And don't even think of just jamming some silicon or 5200 in there .

^^^^^this 100%^^^^

What resin epoxy filler??? Would West marine Six 10 thickened epoxy adhesive fit the bill? Or the G-flex 650-8 and add some cabosil to it? Yea 5200 and 4200 were never in consideration.

Appreciate your help

6-10 is perfect for that.

I used the west systems six 10 on mine and pumped it till it shot out inside. I also used it to seal deck to the hull and got idea from this forum. So far it seems to be holding up good ,only time will tell though

Based on information provided by somebody in the know - who prefers to remain nameless - I now understand the fascination with transom (or any underwater) lighting. It's a secret plot by the fiberglass & gelcoat repair industry. If enough people continue to improperly install these bad boys with poor transom sealing, the revenue stream for the industry will continue for many, many years to come.

Now I ask you, does that make sense or what?