the vacuum advance is a cone shaped unit on the side of the dist, it goes down to a tip for the vac line. if you take the cap off you can see the mechanism it operates. maybe since this is for a boat it didn't have one. i am not familar with them but if it doesn't have it i would think you will need to get a dist with one on it to work in a truck. maybe the boat only opperates at fixed rpm's and doesn't need it. also don't some boat engines spin in reverse rotation? good luck.