Hobie16 Rudder lock down problems

I am a newbie and I have a 1982 Hobie 16 and I am tweaking it. The rudders won't stay locked down while sailing. Then, when I "think" they are locked down, steering is very HARD I am a big guy and in high winds 15 knots its all I can do to is just focus on the rudders. This-my-friend, is NOT relaxing. I have read where there is s'pose to be a 3/16 allen wrench adjustment on the side. No there isn't. So, talk to me.