Most booster cables don't have enough wire size to carry 6 volt system current. I'd suggest going to the heaviest cables availiabe, I believe they're #1 or #2 wire size, on hot and ground, and be sure the connections are clean and tight. Wire-brush the battery posts thoroughly before installing the cables, and be sure the frame or engine where the ground cable installs is brushed bright and shiny. Once you've got everything bolted up solidly, coat the outside of all the connections, battery terminals, etc., with Vaseline to retard corrosion.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!