Just got this from a r/c car site......
For servo-savers, usually they aren't adjustable (unless you're talking high-end stuff) - so normally you just install it, and there you go. It's often a spring-loaded type deal where under normal steering conditions, it's all tight, but if you were to move the servo and hold the wheels in place, you'd see the steering linkage have a little "give" in it so that it won't force the issue and snap something.
Usually the servo saver is either installed directly on the servo gear (instead of a straight arm, it's a servo arm with a spring in it, so to speak), or down the line in the servo linkage (by the steering posts it rests on). They help when you slam into things with the steering, so it absorbs the load with some give instead of transferring it all to your servo gears (damaging them).
For the slipper, it's kind of a judgment call. If you're peeling out and wheely-ing hard on takeoff, flipping over, etc, you might want a looser slipper. If you gun it from a standstill and it feels like it's taking too long to get that torque down, it might be too loose.
I think the rule of thumb is you should hear it "slip" for a few feet on takeoff, that's about it. It's something you just have to get used to - if your truck seems to behave fine on takeoff, you're likely ok.
........... So I cannot really see a use for it on a ship, unless of course you are moving the rudder mechanism further than the rudder detents, but then that would be poor set up, its not as though water would cause any shock to the rudder that can be found on rc cars.
Still go to Hobbyking or RCUniverse type in servo saver into the search bar and they have them by the bucketload.