Cheech, I live in the Pine Rivers Shire and spoke to the council today (moreso because I had the bright idea of trying a few more marks out in the Bay this morning - bloody decent swell for a 6m tinnie, that's for sure - and only caught undersize squire). Anyway, I had them confirm that it's OK to flush outboard from the hose and also to hose the outboard off after washing (with sponge, etc) but boat and trailer has to be done with a bucket. I queried the issue of safety (brakes on trailer, etc) but was advised that buckets only - no hose on trailers. Their best advice - go to my closest car wash.
I've gotta agree with Hi-Yo and SCOTTYGC - using a trigger hose would definately use less water but I suppose the "decision makers" figure that using buckets will put more people off. That said, using the car wash today cost all of $6 using soap and clean water to rinse off. Then it was home to flush the outboard and tidy up on the smaller bits. I scrub the boat down whilst still on the water to clean most of the grime off - that way, it's only really salt that's left behind - easier to clean up after rather than fish guts/blood.
If anyone has any advice contrary, I'd love to find out - I should have asked for written confirmation but I've never been blessed with smarts.