Some programs may be called "Marine Maintenance and Repair."
Some schools combine boat repair with other programs, such as motorcycle repair or small engine repair.
In most on-the-job training programs you need to purchase your tools. As an experienced mechanic, you may have several thousand dollars invested in your tools.
Going into business for yourself is often possible in this field. But a large number of small businesses fail. You may want to take some courses in small business management to improve your chances.
As boat engine technology continues to advance, you will need to keep your skills up-to-date. Expect to take classes throughout your career. Often equipment manufacturers teach these courses. The good news is that usually you can expect your employer to pay for this training.