Deck fill fitting frozen

[callistov42]

I didn't use my deck fitting to empty my holding tanks for 14 years while the boat was in the Caribbean. Now that the boat is home and pump outs are available, I want to open the forward waste pump out deck fitting but it isn't moving. I tried putting some oil around the thread area and letting it penetrate for a couple of days but no luck. It is stainless with two small holes for a spanner and a large slot between the two holes. Any thoughts on breaking it loose or just replace it?

[Orion Jim]

If you have access it would be easiest to remove the deck fill and clamp it in a vise so you can apply heat and coax it apart with a breaker bar. Barring that I was able to free mine by using a Groco bronze deck plate key which has studs to fit those holes properly and applying sufficient force with a four foot section of heavy wall pipe. I learned my lesson and lube the threads annually.

[TeddyDiver]

There's rubber gasket seized it fast. Try oil and steam then raw force..

[ttex]

Use more force. Put a good solid key on and open it with a pair of channel lock pliers.