Hi Brian,
Good to see you back. It looks like the effect is fx_wake.fx. You could try wakes from other amphibs you've got. Remark out the wake line in your aircraft.cfg file and copy/paste the wake line from the plane with a better/showing wake into it.
I suspect that fx_wake file may not be showing in P3dv4, because I seem to be missing some ship wakes lately. Anyway, the aircraft.cfg effects section is where you'll find the appropriate line to edit.
So, go flying and load amphibs or boats and view their wakes. Choose one that looks good, then copy paste it's wake effect line to your beaver's config file. Finally, go out and test it on some water to see if it shows, and looks good.
That's what I would do.
(I haven't checked my MV Beaver's wake, fyi) Going to do that now, ...
Actually, my fx_wake.fx file is showing as intended.