This is the Aqudrive 2.0 main propultion unit that I have used for a long time.
It features a powerfull bruched motor that has 2 shafts one for the waterpump and the other for the gear drive.
The pump has 3 seals and is a gear pump so it does not matter the direction of operation.
The gear drive has 2 ball bearings a nylon main gear and a brass pinion gear in side of a sealed houssing making it possible to grease the drive with a an out put shaft of 3/16in,built in thrust bearrings.
Three ratios are available 2.5,3.0 and 3.5.
Very smoth 12 volt operation and plenty of top end power can rasily turn up to 4 inch scale props.
Just specify the one you need, and parts are no problem.
Installation requires a sealed coil on the exterior of the casing or open to the sea with a filter.
$ 70.00 plus postage