SJ radar can be hit or miss with surface contacts in rough seas... at least with the small ones. I will pass over an area on the scope manually several times knowing a target is at a certain range and location and sometimes it shows up and sometimes it doesn't. On the A-scope you can see the spike fade in and out if you keep it focused on the target. I have only experienced this with sampans and fishing boats so far - lots of them around Guadalcanal.
Even more frustrating was that the sampan made a big spike on the A-scope at 40,000 yards. I thought maybe I had a lone cruiser at first. As we got closer, the A-scope amplitude got smaller.
Also, a word of caution: the radar operator doesn't always report contacts. Especially n00bs. I had a destroyer almost blow me out of the water at about 5,000 yards in the New Georgia Sound at night, because he didn't say anything. So, now I make it a point to look at the screen every hour for several revolutions. (Lousy look-outs didn't say anything either).
I've noticed that the crew is mediocre on the first patrol, regardless of how good their stats are. By the second patrol, they are usually a lot better at their posts.