After so many sea miles with only relatively minor breakages, we've finally struck something more akin to disaster last night when our Autopilot course computer blew up just before dinner.

Whilst we have a spare linear drive motor unit, we do not carry a spare course computer. With Helen steering in darkening conditions charging down waves at 10 knots, I frantically retraced all wiring down in the dark lazarette using the multi-meter to try to identify the problem.

Jesse was wonderful as he finished making dinner, -sausages and mashed potato - and served up dinner for the kids then washed up the dishes. Zoe read Tyler a book and put him into bed.

After reducing sail and slowing our speed somewhat, I called Raymarine back in Sydney on the Satphone and they talked me through various tests I should perform to see whether the problem was fixable. Unfortunately, the problem is not fixable so we will have to hand-steer the last quarter of this leg to Fatu Hiva (the Marquesas Islands, French Polynesia). To put that in perspective, Helen and I have to share the steering 24 hours a day over a distance longer than the Sydney-Hobart race. It should take us about four days so we'll reach our destination on Thursday evening, or we may have to stand off until Friday morning.

After almost four hours on the wheel, Helen was exhausted so I took over for a couple of hours while she slept in the cockpit alongside me. We alternated like that all night and I guess we'll continue to do that for the next four days.

Our friends on yachts near us have stayed in radio contact and Stewart on Rhiann-Marie, the magnificent Discovery 67, has offered to lend us his spare course computer when we arrive in Marquesas. If that works, we'll be fine as I'm sure we'll be able to arrange for a replacement to be available in Tahiti when we arrive there in four weeks time.

Other than that, we've had a wonderful passage and we look like making Fatu Hiva in 15.5 days which is very good. I hope to report better news in the next update.