What kind of certification do you need to become an tug boat engineer?

So you want to be a tug boat engineer. This question depends on the type of tug you want to serve on. Tugs come in many shapes and sizes, not all of them have engineers aboard. Generally when the Certificate of Inspection (a document issued by the US Coast Guard) requires engineers they must be present. In the case of uninspected vessel ie small tugs there will generally not be an engineer.

So you find a tug that requires an engineer, you will next need to find the horsepower and type of engines she has. Then you need to get a US Coast Guard license that would cover that horsepower and type of plant. For example an engineer on a small harbor tug would require a different license than an engineer on an oceangoing steam tug.

The best place to start is to get a job with a tug or towing company as a wiper or oiler, which is an entry level position, then you can accrue seatime, and study for a license exam. You may have to attend a school, as engineers are required to be knowlegable in all aspects of shipboard systems, such as electric, steam, fresh water supply, refrigeration etc.