When I fry fish it's not spicy or crispy. I  marinate it with fish masala, lemon juice, and garlic paste for 2 to 3 hours. How long should I marinate to get a crispy and spicy final product? 
Coat the fish and fry at high temperature I'm making some guesses about your brief question, but I don't think the length of time the fish is marinated is going to make it crispy unless moisture is extracted in the process. What I would recommend is, after marinating the fish as you have, dust it with flour that has the ground spices you like mixed in. If you are frying in oil, get the oil hot before adding the fish and this will help take moisture out of the outer layer making it crispy. 