The advent of affordable 3D printing technology has really changed the landscape of what can be created.   While it might not be the fastest way to create thousands of parts - for the custom creation of small scale parts it is a game changer.
When I was building a 1/10th scale model of the 1983 Miss Renault I could not find any source for the scale (dummy) motor.  I managed to construct a fairly decent turbo Allison - but - it just lacked the kind of detail that can be created with a 3D printed part.  When a friend of mine started building a 1983 Atlas, which also needed the turbo Allison I finally jumped in, bought a 3D printer and started working on the CAD models for the motor.
The 3D printed parts here were made on a FolgerTech Prusa I3 printer, and printed in PLA.   While the printer is limited to an 8x8 inch build area, that is sufficient for many scale hydroplane parts up to 1/8th scale.   Recently I also got a Flashforge Creator Pro, which has a 9x6 build area and allows me to create 1/6th scale motors for the first time.
The scale parts, such as the turbo Allison motor, come as kits - a set of plastic parts that you paint and assemble into the scale motor.   While some cleanup, sanding and finishing are required, the part fit together pretty nicely and assembly is quick and simple.
The motor image on this page shows a rendereding of the turbo Allison model in the design system.  This is always a work in progress, so as time goes on I will be adding more detail features to the models as well as making other scale bits and pieces.
Go Fast - Turn Left
Here is a picture of the typical set of parts for a turbo Allison, where they have been painted and some of the components have been assembled.   There are about 40 separate parts to make up the turbo Allison model.  That is basically driven by making the parts "printable" with minimal overhangs.
Anyway - there you have it.  You combine a boat guy with some technology and you get boat parts.  I hope some of these parts can help make your next scale hydroplane a great model.