HO Scale Lifeboats (and some larger vessels, too)

[Sumpter250]

The only thing you didn't have to model were cowl ventilators, not really sure how I'm going to scratch build those, the commercial ones I've seen are far too big even for a freelance. Any anyone :?: .

Google: Scale model cowl ventilators You should be able to find some that are the right scale, or if nothing else, "close enough for Government work"
Looking at the linked photo of the car ferry, I didn't notice any cowl vents, but would have to assume they are located close to the four stacks, and hidden by the rail cars.
If all else fails, the best answer is to make a master, mold it, and cast the parts from the mold.
In any case, I'm looking forward to seeing this built......there's always something new to learn, and one of the greatest places to live is on the sharp leading edge of a learning curve.