Not a bad consideration for NY Harbor.
Being dead in the water in the traffic of NY Harbor is not a situation to be taken lightly. On the other hand installing an outboard motor on a 30 foot boat is costly and cumbersome. I would invest my money in rebuilding the inboard diesel and insuring it is in tip top running shape. I clean my filters, water separator, change oil, cooling hoses and impeller regularly. Every time will check for starter performance and noises and monitor alternator output. In years that I have been sailing have never had a diesel engine fail me. I know is not a matter of "if" but of "when" but just work the ods on your favor. Other sailors have listed the drawbacks of out board engines.