That's a good point - I think our Garmin Map 76 was doing the same. That said, our ground crew timed us from start to finish and the GPS distance measurement is reliable - so our average speed remains the same - 14 mph.

The GPS unit hangs upside down in it's waterproof bagged, stuffed down the crews life jacket - I think this is what makes it loose reception. Next time we'll fasten it to the mast.

Maybe this is the reason I kept losing reception

Is that a GPS in his pocket or does he just "like" the skipper???

Or, couldn't he wait for the "porta potty".

I was out in my friend's big monohull this weekend, and kept an eye on the GPS while I was driving. It didn't come up with any strange readings while I was watching it, and our max speed was nothing surprising, around 8 knots as expected. This would seem to support the idea that keeping the GPS upright (e.g. strapped to the mast) would elminiate any inaccurate readings. I can't test this on my own boat because I can't afford a GPS. Has anyone else tried this?