They're not really serviceable. You can stick a finger in to smear some grease on the ball but you can't open them up.

I like that Marelon isn't subject to electrolysis, but they're not as strong as metal. I wouldn't use them on a boat that's left in the water in a northern winter. The original designs had a problem with the handles twisting off, and the newer ones still flex enough when turned that I don't have a lot of confidence.