If you do it like this, you will need to run a bonding wire from the mounting bolt of the zinc, to the next available bonding wire, usually located under the power trim unit anode. If no bond wire is available on the engine, run it directly to the negative terminal of your battery.
To make the bonding wire, use 1/16" diameter stranded stainless wire, and crimp a ring terminal on either end.
On my Triton 1650, I mounted (2) 1/4" bolts through the hull, and used really long ones, then secured them with lock nuts and washers. The excess amount that sticks out the back of the transom (about 2") acts like a set of studs, and this is where I mount my zinc anode, by installing a strip of aluminum to the anode itself as a backer plate, and then installing the strip to the 2 studs that stick out. This way, any time I need to change an anode, I never need to re-apply sealant, etc, it's a simple matter of removing 2 nuts, then remove the anode, change it, and re-install.