You owe 40 years on the financed portion.
Note that the cheapest end is about MCr30...
There is a sidebar on page 137 of the MGT CRB that mentions how to handle it. Putting it into a more clear process.
Step 1: figure out total cost of ship.
Step 2: Figure out total shares.
Step 3: Subtract value of step 2 from value in step 1. This is the financed amount.
Step 4: monthly payment = financed amount/240.
Note that this IS different from other editions' mortgages. In other editions, there was a 20% down requirement, and the payment was based upon the whole price, not the financed price, so the actual payment was 1/192 of the financed amount.)