i have a prop shaft from a bravo one that is bent 20 thousandths. I'm looking into taking it to a machinist and having it straightened. I already fixed the drive with a different shaft. My question is, is my shaft worth anything once i get it straightened or at least i will keep it as a spare.

If it bent once, it will bend again. Send it to the dump.

I've seen them straightened while still in the drive and continued good service. Just my experience

Can't imagine the abuse the drive housing, bearings and carrier will incure while beating on the shaft trying to straighen it while still installed. Maybe as a last resort.

Have you ever seen a prop shaft break?? The prop has a tendency to go where it shouldnt.. But they end up at the bottom of the lake.. Now my thought is.. prop is worth more than saving a prop shaft... They can also go up before they go down,, then it makes a mess out of the case, etc, etc.
I would not trust a straightened shaft. I would not reuse, it just isnt worth it..

my .02

Second the above. While you are at it, better check the vertical shaft too ... they tend to twist when the prop shaft twists.