Psychological Thriller about one legged murderer

[Alan]

Desperately want to know what the hell was this movie....I saw this movie once -definitely a Psychological Thriller- something from the early eighties (or late seventies) which was about some girl who ends up with a guy who is a murderer. She bluffs her way out of a certain death. A scene follows that is really something else! She has sex with him (almost explicit scene, but more intensely erotic). At the end of the film she kicks the fellow overboard (leaving a leg prothesis behind). Sounds weird?? Well, I know!