Well, unfortunately you will probably lose a friend over this one but you may be saving lives including your own. The best way to deal with it is to just be honest with him. Tell him the truth and express your concerns, if that does not work and you are comfortable approaching the owners on your own then do it. One thing to remember though if this backfires on you it is not the best time to be looking for a job right now...you need to ask yourself is it related to personality differences between the two of you and this guy is just a tool or is it related to safety. Safety always takes precedence in my book and if you are the captain you call the shots where that is concerned. Good luck with this one !