Name of a murder mystery/ kidnapping book!!??

Question

ok. there is this book it is about a couple they were selling their boat and these ppl. came to look at it so the couple took them on a test ride and the ppl. that were buying the boat held them at gun point and murdered both of them on the boat. So if ne1 can tell me the name and author plz. My aunt knew the ppl. that were killed and told me it would be a good book to read. it is kinda of an older book so its not new..

Answer 1

Try to Google the main characters.