I tried poaching and in my opinion it was just a waste of time.
Had a motorboat (biggest carry weight) and a truck near a coast. One trip made me only about 75k. Even if it doesn't need processing and the distance between poaching zone and turtle dealer is not big, time that adds up is huge. If you are alone, after leaving truck near the coast you have to run back ~4.2KM. Finding turtles to kill is also a hassle, because you have to wait for them to spawn. Luckily they sometimes spawn in groups, but you still need loads of them to fill your backpack.
There are also another two large drawbacks. First is that it's illegal. Organized Crime Police can easily spot your boat floating in the water and just make an ambush for you at the turtle dealer. The second drawback is that you have to drop your old gear, so you could wear the diving one. If there was a way to safely store your items, it wouldn't be a problem. The best option now would be to store your old gear in a vehicle that is hidden or your truck and get it back when you are finished. In this way you would only loose your diving gear.