Centerboard trunk cap refinishing

I'm refinishing the centerboard trunk cap. At the one end (centerboard opening/front) there is a crack that is about 4" long and at most 1mm (1/32") wide. The crack doesn't seem to impede the sturdiness so I'm thinking of reusing the wood. Should I use a filler to fill the crack before refinishing it or will the sealer and varnish fill it? I'll be using Interlux Inter-Prime Sealer #1026 and Z-Spar #2015 Flagship Varnish for the refinish.

Claus FS5074 Ames, IA