Having some level of experience in fire training in various scenarios over a number of years, I highly recommend that you take a commercial approach to generating your smoke, rather than a homemade recipe that compounds your liability. Any smoke you generate from a homemade smoke bomb is likely to be considerably toxic, and should be avoided. Fire fighters would not enter a smoke-filled boat to attack an active fire without the appropriate safety gear which would include correct breathing apparatus.
You can purchase smoke cartridges of various sizes, colours and burn times, and these are designed for this very purpose. Examples can be found using a quick search for fire training smoke cartridges: here, here and here are examples from companies that I in no way endorse. They are pretty cheap for the effects they produce. I use the 20m3 burn capsules for fire fighting training with vehicle fires - these have a burn time of about 5 minutes, and they are very authentic, apart from limited smell. The smell from a fire in a boat is likely to be an acrid toxic affair, quite unlike your typical woodfire smell, so you would be best to avoid this. For better effects, burn a couple together, and you can get burning cups with electronic ignition that allows you to remotely activate it whenever you are ready.
Another option for generating limited visibility that is frequently used is a smoke/fog machine that is used for theatrical smoke and at nightclubs. Search for fog machine or smoke machine. Here is an example - again, I have no affiliation with this company. I have used ones that have come off ebay, and they are very cheap, but do the job nicely. I have used these a lot simulating structural fires and vehicle fires, and they can produce great amounts of 'smoke'. You need to take care that before any water is applied that the smoke machine has been turned off and removed well aware from the area. These also work very well for using with ram fans to visualise wind flow patterns through buildings/structures to understand convection flows and the path of travel for fires.
Be sure to read and understand the SDS of all materials before you use them in an enclosed space such as a boat, and ensure you have a plan to sufficiently ventilate any space between fire drills and afterwards.