The SARO drive consists of a transom plate, a propeller shaft with a U-joint, a surface piercing propeller ( dipping less than half of it’s diameter under the boat ), a couple of bearings and seals, a rubber bellows and a housing. No oil filled gear box hangs in the water.

It is, by now, common knowledge that a propeller just dipping into the water line by half or less than 50% will have the same “grip” in the water as a full propeller, but creates considerably less drag. By looking at a prop, it can be recognized that a large portion is not blades, but a hub and shaft, plus housing. All these components create drag and try to slow the boat. A surface prop does not have any components that drag, thus the boat goes faster. The slight disadvantage in that the prop sucks and pulls air into the water, instead of blowing a solid column of water out. It pushes air with water and reducing the density of this mixture.

SARO has found a solution !

SARO invented the tunnel drive. This is really a half a tunnel, or hood, over the top of the propeller. The tunnel reaches into the water on both sides and prevent air from being pulled or sucked in. Now, only water is filling the tunnel, and a solid stream of water is accelerated to push the boat forward.

This propulsion system is between 10 and 18% more efficient than conventional out-drives or fixed props. The greater part of the improvement is due to the surface piercing and tunneled prop system. Some of the improvement is also due to the lack of beveled gears. These gears, used in typical out-drives, normally create a 5% loss of power. Tests have revealed increases of speed from 45 to 55 miles per hour without changing engine or gear ratio.

The SARO drive steers hydraulically and it lifts like any other out-drive. However it has the tunnel, which thanks to its shape, also acts as a trim tab. This allows it to level the boat to the position for best performance. The prop and drive lift entirely out of the water just like an outboard motor for beaching the boat.

The SARO drive uses a simple marine gear which is flanged to the engine. The gear, mostly ZF which is an STD product, is easy to maintain. It is not exposed to salt water and operates in a friendly environment. The SARO has only 3 moving parts and is a very low maintenance product. Since the SARO mounts much higher than any other drive and the prop only dips under the boat by less than half of it's diameter, the SARO is the best way to go for shallow waters. If the hull makes it, the SARO TUNNEL-PROP will!

an elance service Provider