A true starting battery has many small plates so that it can put out more amperage over a short period of time. A deep cycle battery has thicker plates and is designed to produce less amperage at any given time but is designed to be drained to 50% many times. While these are the design parameters you still can use a deep cycle battery for starting. The amperage required to start a modern diesel can be surprisingly low. Unless your engine is very hard to start you should have no problem.