The Lewmar lever system has a "natural" neutral position, in between forward and reverse. It is easy to feel it when moving the lever.
This is assuming the cables are moving freely.
There can be an other issue, if the neutral position of the lever does not fit with the neutral position of the gear box. If his is the case, it is possible to adjust the cable on the gear box side: Disconnect the cable, make sure the lever is in the middle, then check the neutral position on the gear box and adjust accordingly the cable.( It is to my opinion very instructive to understand how the gearbox (I do not know the real name...) functions, in case the cable breaks at sea, to still be able to move forward and reverse by hand from inside the boat).