replaced one battery, was completley dead. Now intermittent no start. Boost and it runs fine until it dies. Alt is charging as well. Is there a battery isolator on these, if so where is it ? Thanks dan.

Always replace both batteries if one dies.

Check all cables, clean them good and make sure the connections are tight. I just talked with someone with intermitten battery problems and he bought a new starter even and all it was was a loose wire. Check all grounds for corrosion.

I had dual battery set up on my 1992 Chevy and replace only one battery and never had a problem doing that. But do get the other checked out as it may be going also.