I agree with Jeff on the
wheel pilot computer issue. I have used 4000''s for about 13 years starting with the first model. I now have a 6000. I think the main differece is not the strength but the sophistication of the computer. In a sloppy following sea the boat would sometime start to oscillate with the 4000 since it did not anticipate or learn as well. The new 6000 seems to due a hugely better job of this. With the addition of a gyro, course keeping becomes near perfect in challenging conditions.