Never had this problem before...

[Skullcracken]

I have been running in slightly rougher water the past week. Two of my boats lost the screw that holds the pivot block on the arm of the rudder (not the set screw that holds the control rod. Twice had to fetch my boats because the rudder is just "free flopping" and detached from the pivot block. Don't know why this is happening. If I tighten it down too much the pivot block won't "pivot" with the control rod and the steering sticks.

[Skullcracken]

Also, how can I buy this screw without buying and extra rudder system. For that matter, is there anywhere to order sets of set screws for couplers etc and other small screws for specific boats.

[monojeff]

Check local ace hardware I know mine has a decent assortment of small hardware.
Otherwise you can always depend on mcmaster.com

Are you using locktite on the screws??

[HYDROJERRY]

when you lost the screw did you loose the steal rod that connects the rudder to the bracket if so you can just use a drill bit just find the wright size drill bit and cut the drill part off and use the smooth shaft part,,,

[siberianhusky]

You're talking the push rod holder that screws to the rudder arm from the bottom? Pushrod slides through and a screw on top clamps it down?
I've had problems before with those, I think after a while the threads wear from the pounding of the rudder, the screw is much harder than the body.
I prefer Z bends or a Dubro 4-40 threaded ball link if I'm replacing something like that.
Or loctite on a new one.
Z bends are my favorite, one less thing to fail, only the clevis on the servo end. I like the metal dubro 4-40's with a piece of large fuel tube as a keeper.

[Boaterguy]

Loctite is the best, I always had that problem, you can even use non permanent, and not tighten the nut fully. I Bench tested moving the ruder back and forth for about 5 minutes and the nut didn't move.