Additional info follows.
I just bought a used 250 and want to start it before I intall it.
I just hooked the positive on a battery to to the starter and the negative to the block and used a remote starter switch.
The starter keeps cranking after I release the button.
Is it wired incorrectly or maybe it needs to be shimmed?
Does it take any power to disengage the starter or should it just release though spring pressure? Any suggestions will be appreciated.

More info.

I forgot to mention that I took the starter out and "bench" tested it, it seemed to work fine. The gear came out spun and released. So I am guessing I had it wired correctly.
Also a powerglide is connected to the engine but I don't believe this would contribute to the problem.

Would it seem that the starter needs to be shimmed?