![]() ![]() Inboard jets are slightly more favourable in this respect, but comparing like for like with an outboard with a prop and the same outboard with a jet conversion, you’ll generally find about a 30% loss in horsepower in the jet version, largely because the path the water takes from the intake to the jet exhaust is somewhat convoluted, making for an inefficient transfer of energy.Īs touched on above, in much the same way as inboard and sterndrive/outboard propeller drives, jet drives broadly come in two distinct flavours: inboard and outboard. The major difference between propellers and jets is in the output performance. How Does Jet Drive Compare to Prop Drive? If the boat then loses control you can imagine what happens to the person behind the boat. To make matters worse inboard jet drive boats don’t feature rudders or skegs, making them far less stable in the water, and consequently far more likely to be pushed off course by the action of the person being towed pulling hard on their towing line. ![]() Jets produce a a very aerated ‘bubbly’ wash that can easily throw a skier/boarder off course. However the actual performance for anyone being towed by a jet boat is far from ideal. Jet drives are certainly safer than props from an embarkation/disembarkation point of view for water skiers and wakeboarders, in as much as the engine can safely be left running at all times without the risk of anyone being seriously injured by the incased impeller. This make jets a far less comfortable ride in more challenging sea states. This enables you to tailor the trim of the boat to suit the conditions or speed, for example by trimming the bow up to cope with a choppier sea or travel up on plane at a higher speed.įixed jet drives do not have this luxury, and most outboard jet drives are usually mounted so high on the transom that trimming is ineffective. Outboard motors and stern drives have the distinct advantage of being possible to trim that is to say you can tilt the engine or prop with the effect of raising or lowering the bow of the boat. This isn’t as effective or efficient as simply reversing the direction of rotation on a normal propeller, and the results can be sluggish and difficult to control. Jet boats aren’t too hot when travelling in reverse either given the jet can only be directed aft, you’re reliant on the redirection of thrust as a result of lowering the deflector plate over the jet exhaust. Thus, lower speed = poorer directional control. The reason for this is that the effectiveness of the directional control of the ‘jet’ (the flow of water expelled by the jet that provides thrust) is more or less proportional to the speed. Whilst jet drives operate well at speed, when it comes to travelling slowly they aren’t great at all. Just be sure to hold on tight if you ever do this! Why so? Well by slamming the deflector plate over the jet stream and immediately reversing the flow of water you get a much more immediate effect than having to wait for a prop to get up to speed in reverse. In addition if you ever need to stop quickly, then in theory a jet drive is the best means to do so. As mentioned above, they’re great in shallow waters, but inboard jets can also be backed up on to beaches given the absence of any protruding parts including rudders.Īt very high speeds jet drives have been documented as being more efficient than props, and they’re certainly quicker to accelerate. Jet drives offer a lot of practical advantages over propeller driven stern drives or outboard motors, mostly related to the fact that they are safer in conditions where impacts with foreign objects are likely. As such jet drives are perfect for flat bottomed vessels (Jon Boats) used in shallow, rocky rivers, or in applications where personal safety around the prop would be an issue, such as when water skiers climb in and out of the stern of the boat. The impeller of a jet is generally a smaller item than a prop designed for a boat of the same size, and being fully encased, it is well protected from its environment. Well in simple terms jet drives are great, but only in very specific circumstances, much like airboats. Off the top of my head there are 3 ways of propelling a boat, either through the use of a conventional propeller, an impeller (or ‘jet drive’), and aircraft style propellers typically found on flat bottomed air boats used in marshlands where below waterline propulsion is impractical.įor most of us the choice will come down to propellers or jet drives, with props generally ruling the waves in most harbours.īut why is this the case? Why don’t jet drives enjoy the same level of popularity? ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |