No repeater in the Percy Group. The Percy Island Homestead at West Bay on Middle Percy Island 'monitors' VHF Channel 10, and I'm sure would relay an important message for you (they also have a Sat Phone: +61 (07) 4951 0993 )
Also, hopefully any cruising Yachts in the area would be monitoring VHF Channel 16.
West Bay is known as a rolly anchorage.
You have a potential bolt hole if the weather gets bad. The 'Lagoon' at West Bay can hold a number of boats, however is mostly dry at low tide. Cruising Catamarans regularly hole up in there and take to the dry for shelter/maintenance. You could raft two mono's together so they support each other if there wasn't enough low tide holes to float in. Entry/Exit from the Lagoon is tide dependant. Stay on the boats or hang out at the Percy Islands A Frame or Tree House. If camping - the Homestead does request a camping fee of $5.00.
Entrance to the Lagoon;
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Lagoon at High Tide;
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Near Entrance to Lagoon at Low Tide!
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Good Luck. Have a bloody great time guys!
Cheers,