Suggest me a best business to start with no investment

Most all businesses require some investment and generally, the lower the investment, the greater the competition will be for that reason unless you have some rare skills to offer.

A person experienced as you are, in Marine Engineering might be qualified for many things mechanical. If you are in an area with lots of boats, I would print some business cards for minor on-site boat repairs and hand them out to boat owners. Your only investment would be for tools and transportation.

If that isn't possible, how about an on-site automobile rescue and repair service?

Your best bet for minimal investment will be service areas that don't require the overhead of a building and/or other employees until you are sure you can afford them.

Personally, I feel every business requires some investment to start with.The cost may differ.In all these years as far as I know, any business that says no investment has either been a scam or is a trap set for newbies.There are many legitimate ways to make money online.You can earn through internet by writing blogs,articles,ad-sense,affiliate marketing and other such ways.I have been into online business for the past few years,I do reselling business with http://www.goresellers.com ,I chose this business because there was no way to get scammed if we found a legit reselling company.It is very easy to make a good turnover because the cost for each service is fixed by reseller and also it has a fixed commissioned pay for each sale.The customer service and payment is handled by the reselling company and hence I just have to promote the services.