To use this game with three or four players on THEC64, THEVIC20 or THEC64 mini, use the following CJM file with firmware version 1.6.0 or later:
T:Bomb Mania
A:Protovision
X:64,pal,accuratedisk,driveicon,fullheight
J:1:JU,JD,JL,JR,JF,JF,1,2,JF,A,B,C,JF,,
J:2:JU,JD,JL,JR,JF,JF,F1,F2,JF,1,2,3,JF,,
J:3:JU,JD,JL,JR,JF,JF,F3,F4,JF,4,5,6,JF,,
J:4*:JU,JD,JL,JR,JF,JF,F5,F6,JF,7,8,9,JF,,
Name the CJM file the same as your D64 file, so if your disk image is called BombMania.D64 your CJM file with the settings above BombMania.cjm
The firmware version is available to download here -> https://retrogames.biz/thec64/support/upgrade-thec64