dog growls at owner

Question
My dog is a 3 yr. old cockapoo and he has always been skittish but he growls when reprimanded and hides and also marks. We have another dog who we had first. Neither dog is neutered. (both male)He also if he is really scared will snap and bite but not hard. I've always owned dogs and have never had a problem training them but this 1 has me stumped. The marking is out of hand.He is ruining new furniture. Any suggestions? I hate to get rid of him otherwise he is good and affectioate dog.

Answer
Hi Stephanie,   Unfortunately, there are alot of inherently shy dogs out there.  These dogs were usually shy pups who's temperament was decided on the day their parents were mated.  This seems to be a relatively dominant trait that runs down the line.
    However, your dog (shy or bold) needs a large dose of basic training 101.  Here goes;  All dogs should be crate trained. they should practice this every day.  All dogs should be taught to stand tied for a reasonable length of time.  This requires a serviceable collar & a substantial chain (not a foo foo one).  All dogs should have a place to call their own both inside (a crate) and outdoors (a kennel or a chain) just running around loose in the yard doesn't count. It might have passed 3 years ago, but not with a problematic dog like yours.
    With all this in mind, this dog should never be allowed to run unsupervised indoors or out.  Every free period, when he's not in his crate, or kennel or on his chain, should become a supervised training session.  Clean up all his accidents with a neutralizing enzyme type cleaner.  Make sure your other dog is not adding his two-cents worth either.  Don't tolerate him kicking up a fuss when confined to his quarters.  
    This dog is only three years old.   There's plenty of time left for him to straighten out once he learns what's expected of him.  I will bet his growly temperament will settle down some while you're working on all this. He will begin to be more confident as he learns his job & realizes he's pleasing you.
    These things don't just happen overnight.  These training methods are time tested, but they require real work & some outlay of capital for equipment.   This small outline will probably take a year to implement & call the dog "finished" on it's conclusion.
    Good Luck Stephanie,  & Thanks for asking!   Rob