Pettit Ultima SSA..works good on my trailered boats both past and present...
can get 1 gallon under 100 bucks...2 coats of course!
I bottom painted my 20 foot Shamrock..had existing bottom paint on it...took 2 coats and had more than a 1/4 gallon left...8' beam
Painted my Grady White 20 footer with it..2 coats and had plenty...again existing ablative in both cases...1 gallon might do the trick for you..depends on coverage of bottom paint you select
Obviously stay away from hard antifouling!!
-Fred