I'll look through my Mare Island books tonight. The ones on the Revell kit are torpedo loading cranes. See how they are just above the hatches. It's function was to set up the gear and position the torpedo down the slide using rope falls.. It certainly wasn't capable of picking up a torpedo.
I recall seeing pictures of them stowed flat on deck, and also missing. I'll try to find a picture of one sailing with them erected, but I doubt they were.