Transom construction

I just enlarged a hole in my transom above the water line so my new sonar transducer twist lock fitting could fit through. I'm just curious if what I'm seeing through that hole is how the transom is built all the way down to the bottom of the boat. The first 3/8" of the exterior looks like fiberglass or epoxy. The rest is obviously wood. The total thickness is approximately 2". I've attached a photo just in case I'm using the wrong terminology.

Those other little holes are from the old clam shell. The previous owner didn't do a good job centering the clam shell on the hole. I'm going to have to install a larger clamshell so I'm guessing I can just fill the old holes with Marine Tex. Is that the proper way to seal old holes?

Re: Transom construction

Looks like a pretty standard transom to me. MarineTex or 5200 for the holes.

Re: Transom construction

(Big, long how-to-repair-holes post deleted).

Most people use 5200 to plug holes like that, or marine-tex if you'd like something a bit more permanent. The "right" way to do it involves drilling the holes out big enough so you can be sure you're filling them top to bottom, then fill with marine-tex or epoxy/poly resin with fillers.

Having to enlarge holes for plugs like that isn't unusual. Personally I'm leaning toward a large hole way above the waterline with a watertight, removable cover and rubber seals.

Erik

Re: Transom construction

The hole is 1" diameter about 6" above the waterline. I plan on using a clam shell over the cable and filling the hole with silicone sealant. Do I have to fill the hole completely through to the inside of the boat? Or is the first inch or so good enough?

Also is there a better/cleaner/easier way to seal cable through transom installations like these, like the removeable cover/rubber seals Erik mentions?

Re: Transom construction

Take that marine tex you filled the other holes with and coat the inside of your 1" hole first to seal the wood then install it and yeah fill it up with sealant. I'd use 4200 not silicone but it probably doesn't matter.

Re: Transom construction

Don't use silicone on a boat...it won't stay put. Use 3M 5200 (permanent, non-removable) to fill the old holes and, as noted, 3M 4200 to seal the new fitting you install...4200 is removable at a later date, if necessary.