I have one on my boat lift that seems to be a little cranky but I think a good cleaning may fix it.
Any surprises if I take it apart?

Springs popping out when you try to get access to the contact points is never fun.

Just FYI, when Siemens bought Furnas they dumped off the Drum Switch product line and it was bought up by Hubbell Industrial Controls division, you can still get drawings and parts information there.

http://www.hubbell-icd.com/icd/drum/drum4258.asp

It ended up being a silly problem. I literally had a screw loose (but regular readers here knew that)
I tightened up all of the connections and the problem went away. One did show symptoms of heat.

Boy, a blast from the past brand. Furnas!

OK, now I found out what happened to Furnas. Back in the day it made a big splash at the local supply house.
After the splash, they switched back to AB.

Another splash back then was 'ASEA' motor starters and controls. Gone but not forgotten.

Greg:

I had an issue with a Cuttler Hammer drum on a boat lift, ordered replacement contacts. Had a bad time with the replacements; ripped it out & installed a new Sq. D unit, problem solved.

IMHO, doing 'repairs' like a lot of us did 'back when' are falling by the wayside in our throw away culture.

Yup, I was real happy to see this was just a loose terminal screw. I suspect the contacts may be held in there by the same screw as the ring on the wire so they may be replaceable or at least cleanable but when I was sure the only hot spot seemed to be under the screw, I just tightened everything up and called it a fix. Now it has the old snap so I really do think loose screws are also loose contacts.