What are COUNTER-ROTATING PROPS: There is a big difference between these two boats. The first boat shown has one prop for each engine. Each engine spins counter to one another to avoid side effect. If both props spin the same way in forward, the stern will drift to one side, making a difficult to handle. The other vessel has two engines with two props each. Each engine has its own counter rotating blades. #howtoboating #howto #boating #propellers #props #engines #blades #captain #sideeffect #wal