Theres a couple of shoals on the oposite side of the gulf. I think one is called Snapper shoal and maybe Larakin Shoal or something like that. On good days when the water movement isnt high these places are good for diving. I found around these shoals there are lots of little bombies, maybe only like 500mmx500mm big bombies but all held big coral trout. Talk to Euge from Mackdog tackle, we used his vibes that he sells, work brilliant on trout.

Cheers Pig 

Have done a little exploring in a 4.5m boat when holidaying  in Exmouth. PLnenty of options in a boat your size, but need to work around the weather every trip. Gulf has lots of options for a feed, alhtough mainly smaller species rather than larger demersals. Whiting, squid and queenies along the Bundegi reef edge (note where the marine park markers are though), any small bommies, particulalry as Piggy says on the eastern side and right up towards the passage island, seem to hold trout pretty reliably. East side creeeks and edges also good for  fun on lures, with mangrove jacks, bream, trevally etc. Can also find those back near town around the marina. Spaniards can be anywhere, in season, and have caught them trolling along Bundegi, around NW Reef at the top and of course along the outer reef edge down the west side. Sometimes just drifting in 30m bottom bashing, a floater out the back works very well. For demersals my best sessions in that area have been on lumps in the 60-100m depths, but you don't need to go far. Can get windy both sides, so checking the various apps and government websites is a worthwhile habit while there

Deciding on west or east coast I check the wind on the west side using the live weather station at Milyering, here; https://weather.aims.gov.au/#/station/8 , plus meteye etc.

The BOM has a beta site for Exmouth here; http://www.bom.gov.au/places/wa/8UNQ/