Can anyone recommend a good place near to Sydney's North Shore to Service a Yamaha Outboard Engine?

Your backyard or garage.

seriously 2 stroke? take you like an hour

Just about any decent outboard mechanic can service the engine.

My brother lives Turramurra, and he uses a mobile guy that, when he had a smaller engine, would come, pick it up take it away and return it fully serviced, for approx 1/2 what people like shannons or huetts charged.

If you particularly want a "yamaha" service centre, you would have to look them up. When I was in the industry about 10 years ago, yamaha had an issue with dealers on the north shore........there was one on the harbour, and next accredited dealer was at Brooklyn!

I believe the guy at Brooklyn had a good reputation.

Cheers