I have a crack where the rudder catch is on one of my rudders. Can I sail with it like this? (see attached pic)

You probably can get away with it short term, but I wouldn't risk it myself...

Remove the fitting so that you can inspect the damage properly. Then you need to work out a way of repairing and reinforcing the split. From the picture, I'd probably cut the surface back to a depth equivalent to 3 layers of glass. Then I'd open out the split so that I could force a mix of epoxy and microballoons in to stick the crack together.

Once set, I'd clean the area up so that the fitting can go back and so that I can proceed with the layers of glass and epoxy. So, next the layers of glass and epoxy go on followed by finishing flat and painting once dry. Finally refit the fitting.

Both of my prindle rudders are cracked like that and have been since I bought the boat 5 years ago. So far they have performed without incident. Last time I fixed dings on my rudders I took out the bolts and tried to get some resin down in the crack. I have always thought it would be a good idea to do a full repair, but I haven't gotten to it yet.

Thanks! I was worried that I would have to try to fix that or replace the rudder...
How much catch should the rudders have? Should it be easy or hard to kick them up with my hand? I only put the one on and it was very easy to kick up - seemed too easy.

I will repair the crack at some point - i just want to get this boat in the water and try it for the 1st time already. I have had it for like 3 weeks now and have not sailed it yet. I am still unsure of some things but I am ready to give it a go. (light wind of course)

here is another picture

If they are too loose, they'll kick up unexpectedly, and usually at the most inopportune times. You'll want them tight, but not tight enough they won't kick up if they hit something. So, tight enough you can't pull them loose easily, but loose enough that if you give it a good hit with the palm of you hand they pop up.

Rick probably has replacement springs in the online store, but you can try and use pliers to squeeze the loops of the springs back together somewhat. If you get them too tight pry the loops apart with a screw driver.

you have found one of the problems that the crack may cause - The hook may be moving in its socket because the crack opens up a bit under pressure. this may also lead to a 'heavy' helm whilst sailing.
Fix the crack and wind the hook into the blade till the blade almost touches the transom [When its locked down] to get the best feel whilst sailing

I had the same problem and fixed them this way,
I drilled both holes ( rudder cam and pulldown line holes) a little larger than they are suppose to be, about 1/8 larger and also drilled the hole for the pull down line through the otherside of the large hole, so the epoxy would run down the hole and form a little tail for extra strength. Then I filled everthing with west system and redrilled the holes to the proper sizes. It made for a stronger repair than original