Sorry to hear you missed the boat this year, better luck next year.
The theoretical side of Engineering is largely applied Physics with a bit of appied Chemistry, and there is Maths and English in everything!!! So you are certainly heading in the right direction.
If you have time it might be worth looking at some Technical / Engineering drawing, in the UK anyway that is regarded as a basic skill for Engineers, so that you can read Machinery Drawings and make drawings of parts you want repaired or fabricated.
The British/Dutch Merchant Navy Trade Union , "Nautilus International" has an interesting web site,. www. nautilusint.org
The Institute of Marine Engineering Science & Technology has a website.............. http://www.imarest.org
The Royal Instiute of Naval Architects has a web site ......... http://www.rina.orguk/tna
The Marine Society, is an old British charity, that offers distant learning courses to Seamen at all levels up to Post Graduate studies,
There is free on line study material but you have to pay for courses that have work marked and assessed.http://www.mscos.ac.uk
or e: email@example.com
I hope you find the above sites useful.
It is always better to ask a stupid question than to do a stupid thing.