I had a similar experience to Don a few weeks ago.
I bought a new speed log with transducer and thru hull
. The boat had a thru hull
for a speed log, never installed.
The new thru hull was bigger in diameter so I couldn't reuse the original. When I pulled the plug
I realized the locking ears for the plug had completely failed. The only thing holding the plug in was 4 coats of bottom paint
and 2 o-rings. The thru hull and the plug were both phenolic. The ears were the only metal parts
. Corroded right through.
Thru hulls, seacocks and any penetrations through the hull are on my haulout list. They may be "expensive" but no compromising here. Replace them if in doubt. Know where every penetration is on your boat and the condition.
This one was easy to access as it is right under the galley
. It routinely got a "pass" primarily because I incorrectly assumed it was "plugged" and a non issue.
Oh, I also carry a selection of wooden bungs. In the galley