Sherlock: Undercover Dog (1994)

Billy, 10, a dreamer, wants to be taken seriously so he can live with his toy-designer father on Catalina Island. Billy's plans get seriously spoilt when Sherlock, a talking police dog, demands his help to rescue his police detective handler kidnaped by smugglers. But Sherlock likes to keep his talking a closely-guarded secret. So now no one will take Billy seriously until he rescues the kidnaped detective and catches the smugglers...