Hi Mukesh and welcome to the forum. Unfortunately steam for model boats is a huge subject and although we can point you in the direction of certain plant and models you are going to have to do some research for yourself and make some decisions before heading down the path of deciding what you want to build.
No-one can tell you what is the best until we know what type of model you want so your first decision is do you want a launch, a tug, a cargo ship etc..etc... Then you have to decide how big you want it and that will be dictated by storage space and carrying ability etc..
From those decisions you will then have an idea of what your power requirements would be and then you will have an idea of how big a steam plant you need. The big decisions there are where do you want to draw the balance of complexity against ease of use and remember that for complete RC operation of the engine on one channel you need at least a double acting twin cylinder engine. Then do you want automatic feed, automatic burner control, etc.. etc...
I would start off with what type and size of model you are interested in and we can go on from there.