When we aligned the engine in Greece, one of the bolts that holds the engine mounts was impossible to loosen. The mechanic tried all the tricks in his book, but gave up as he did not want to break the bolt, which would have been a big headache.
Seawater had dripped from the raw water pump, directly on to the engine mount, down in to the thread.
I tried many different tools, WD 40 etc. but no success. It was frozen solid.
Back in Sweden I did find some positive reviews of “OMEGA 636 ” oil. It is an oil that is said to find its way in to the thread and loosen up corrosion. Too good to be true!! I was afraid it was another “snake oil” product. But as I had no better choice, I ordered a can.
Back on the boat I dripped Omega 636 oil on the bolt. After a couple days I decided to give it a try. Like a miracle the bolt moved with normal force!!