Dan. Let me remind you that Baskin & Robins makes, what is it, 28 flavors a month?
That said, I'll just inject, as the OP, that my interest is in modeling, not in operating, and consequently I build static dioramas ranging from
1'x2' to (currently in progress) 3'x4'. In these models, everything is foreground and while I obviously have to make many compromises, I'm simply striving for as much realistic detail as possible in every aspect of the scene.
That said, I heartily agree with you that an HO-scale outboard motor is quite small, maybe 3/32" x 1/8" x 3/8" overall. Rather than "scraps of plastic", I'll probably sculpt something out of Sculpey for the body, maybe carve a piece of plastic for the vertical "shaft", and bend a scrap of brass for the propeller. If I decide I want a few of them, I'll probably make a rubber mold and cast them with resin. To be sure, the extent of the detail on the motor isn't great and scale, color and shape are more important than precision details. But it's going to take on the order of an hour to do the first one and I may not even like it enough to keep it. Probably the equivalent of an evening will be taken up in creating the motor(s) I need. But then for a diorama where everything is easily within the viewer's range of study I feel it's definitely worth it.
And, long ago, I did contemplate actually building a layout in a 12'x15' room in the basement. That was in 1972 and it's likely that I might be finishing it up sometime before I die, but probably not soon. And certainly the quality of the trackwork would have been paramount there. But not in a harbor diorama.
Norm