I've got some videos on You Tube so look up Super-Vee 27 then floatsfast, that's me.
What to watch out for. First, check all of the bolts and the prop nut as most of them were over-torqued from the factory and will break stuff, especially the radio box bolts. Speaking of the radio box, it's probably the weakest part of the whole boat as the corners are really thin and subject to breaking there. To help, remove the tabs from the lid then wrap rubber bands over the top then under the tabs on the box itself.
The stock prop is junk as mine broke while (get this!) simply trying to pull-start it the first time as the nut was too tight. Go with one of their Grimracer props, they're nice. The 40 x 53 should do you just fine.
Keep the flex cable lubed. Aquacraft does offer the Grimracer grease but be forewarned, it's stinky but works well.
2-1/2 turns out on the high-speed needle should get you in the neighborhood.
Saltwater isn't good for any boat, RC or full-sized. Wash it down after running with fresh water. Shoot something like WD-40 on metal parts to protect them from corrosion.