6 mo lab puppy crate and soft stool

Question
I have a male 6 mo yellow lab who has diarrhea all the time.  I have been to the vet countless times and nothing seems to be wrong.  The vet has recommended science diet ID dry food, but this is not puppy food, is it ok?  Also, Cash is crate trained and I go home at lunch time to let him out and run around the yard and swim for 20 minutes then back in the crate until after work.  I work 20 miles from home and with gas prices this is becoming a burden. How many hours a day can I leave him in the crate.  I hate doing it but I don't know what else to do.  I also walk him every morning and every night otherwise he is uncontrollable, is this ok.

Answer
Go ahead with the vet's adult chow.  The only debate among the more knowledgeable is how soon to make the early switch to adult chow for Labs and other large breeds.  7 months is the oldest I know of any well informed people feeding puppy chow, and some are weaning puppies on adult chow.  

I hate to see a dog go over 4-5 hours in a crate or not.  Perhaps you could find a neighbor or professional dog walker to give him a break at least some days.  Likely you would need to clear up the diarrhea before a doggy daycare would take him.