The set up in the photo should work. You could buy the components and build a rig like that using a tank cap that fits your motor. For years I used a simpler rig -- two lengths of hose with a one way bulb pump (like the one in the photo) in the middle. It worked ok, but was slow. I've since moved on to a simple siphon, using a 5 foot piece of clear 1/2" hose. Clear hose lets you see how much fuel you're sucking into the siphon hose, gives you more fuel to work with as you're setting up the siphon flow, and reduces the chance you'll end up with a gasoline mouthwash.
I use my siphon between a six gallon storage tank and the outboard's external tank with both aboard the mother ship during refeuling. On calm days I've had the storage tank on deck and the outboard's external tank in the dinghy and it works OK. With care you might be able to develop a procedure that lets you run the siphon hose from the storage tank on deck into the top of your dinghy's engine while it's tethered along side.
I've found the straight siphon is much faster as the flow rate is better than you'll get through the bulb pump. You can also shut down the flow more easily by just pulling the hose out of the storage tank and letting the fuel drain into the outboard's tank. Again, with the clear hose you can monitor things much easier.
PS I just re-read your post and realized that what you might be wanting to do is carry an external tank with you in the dinghy to refill the engine's tank while underway. If that's the case I'd go with the rig shown in the photo with the proviso that the cap that goes on the engine's tank might not be necessary. Just run the hose on the downstream side of the bulb pump into the top of the engine tank and pump away.
An alternative to having to carry gasoline with you is just to fill your engine's tank regularly using the methods I've discussed above, and "don't leave home (the mother ship) without it"....full.
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