raymarine sportpilot

[ortogo]

I purchased a seaward 23 a couple of years ago, it came with a raymarine sport pilot autopilot which operates on a vetus hydraulic steering system.
Recently it has started to play up, when the boat is run on a constant heading and the autopilot is engaged, it starts of as it should, making corrections to keep the boat on its heading. However the corrections become more and more exaggerated, until it is veering erratically from side to side. Two questions really, does it seem fixable, and if not what would make a reasonable replacement bearing in mind I'd like to keep the price sensible

 

[petem]

What head unit does it have?

Have you made any alterations to the boat lately?

 

[prv]

Guessing here, but the increasingly-large corrections make it sound like there's delay or slop in the pilot's action / feedback cycle. I had something a bit like that with one of those horrible plastic wheelpilots, mounted loosely at the end of long cables. So small changes ordered by the pilot made no difference, just taking up backlash in the system, then when it finally took effect and the pilot wanted to counter-steer, it had to first go all the way back the other way. I don't know much about hydraulic systems, but is there some equivalent effect, perhaps from leaking fluid or softening hoses?

Petem seems to be hinting at compass deviation from changes in the boat; I've had that too (steel beer cans next to the pilot compass!) but the effect was more the opposite, it failed to notice when it was going off course and didn't correct much at all.

Pete