Volvo Penta was first to come out with a sterndrive with a single boat propeller in 1959 and they were first with a sterndrive that has two counter rotating boat propellers on a single prop shaft in 1982.
The advantages of a sterndrive with two boat props are much less slippage that gives a better bite on the water, improved low speed steering response and less vibration. This system also gets the boat up on plane quicker and keeps you on plane at lower speeds than a single prop sterndrive. Reverse maneuverability is much better also.
Volvo Penta’s Duoprop sterndrive is used with gas and diesel engines up to 380 horsepower. It has an electronic trim system that trims the lower unit automatically to predetermined positions. It also has a one of a kind hydraulic steering system that uses external mounted cylinders. Either aluminum propellers or stainless steel propellers can be used but you cannot use one of each on the same sterndrive.
The Mercuiser Bravo III two propeller drive came out in 1993. You can also use aluminum or Mercruiser stainless steel props. Some unique points of the Bravo III are an oil monitoring system that has an alarm that goes off if the oil level gets too low. A trim switch that limits the angle of the drive while under way so the u-joints will not be damaged by too much binding. Bravo III’s are available on gasoline engines with as much as 525 horsepower. Mercruiser has more service dealers than Volvo Penta and repairs and replacement parts can cost less.
Both systems use a cone clutch for smoother gear shifting and either one would be a good choice if you are interested in a two boat propeller sterndrive.
Dan’s Discount Propellers offers boat propellers at huge discount prices for both these drives. For a price quote please call us at 1-800-573-5533