Hi Guys from downunder,
I'm just trying to get back to my boats after a long break while I was totally involved in running my model manufacturing business here in Aust.
When I started with my 1:24 Scratch built Tug, Iron Cove, back in 1982 ( and she's still in working order ) I chose to use a 12v Car Heater fan motor, the origins I can't quite remember, although I'm thinking Ford Falcon. It's around 75mm diam and and has tons of guts!
These motors are smooth running and are not real hungry for amps if run at higher speeds with a belt drive reduction. The Iron Cove runs a 6" x 4 blade home made prop, and is easily capable of towing a dinghy with human passengers aboard.
I make my own pulleys, generally out of either aluminium, or Acrylic ( perspex ), and turn a half round groove which accommodates either Std 1/4 inch "O" rings or ideally Redthane belting which is a polyurethane round hollow section and uses aluminium joiner studs. It lasts forever, as it doesn't perish like the ordinary " O " rings. And you make it any length you want!
Where I started to go with this, was that I also use motors from 12v Electric Car radio aerials which are cheap to locate and are more industrial than a lot of the off the shelf high speed asian built ones.
One of the best motors I ever came across are the 12v Bosch 12 pole heater fan motors out of our early series Holden Commodores, read Opel Senator, from the early 80's. Just so smooth and efficient, and I have a pair mounted in my unfinished 1:24 Sirius Cove.
If anybody wants any further info, just ask. I can't talk about RPMs and stuff, but what I do works!
Ian.