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Jun
But it is between 35 and 40 knots that the gap widens. Lots of fishing guides use them in shallow rocky rivers.
Marine growth can be a real problem with that.
Jet drive outboard vs prop. Because it extends below the keel of the boat the outdrive and its propeller are susceptible to damage if they impact the bottom or an obstruction in the water like a rock or tree stump lurking just below the surface. The propeller can also be a hazard to swimmers behind the boat. A sterndrive also requires more maintenance than a jet drive.
The jet boats are also faster both topping out at 51. Mph while the outboards reached just over 40 mph. The jets are clearly quicker.
The outboard jet because of the inefficiencies of the design reduces your effective horsepower by about 25-30. Therefore for example if you replace the prop lower unit of a 100 hp engine with a jet unit it will be putting out at most 75 hp at. Comfort - Compared to propeller-driven systems jet drives greatly reduce on-board noise and vibration levels.
Jet drives rotate at higher speeds than propellers and the impellers are encased in precision-crafted housings. Jet outboards and boats are used a lot in the upper west coast rivers and Canada. Lots of fishing guides use them in shallow rocky rivers.
You lose typically 25 of hp from a jet vs prop. Ie 100hp prop boat is 75hp jet. Jets are notoriously inefficient.
And weeds are the jet boat drive worst nightmare. Tunnel prop will get you by on 85 of the water around here but that 15 may keep you from going places you want to go. If you go with an outboard jet just make sure it has a stainless steel impeller.
Me Im saving for a jet myself and when I buy one it will be a Mercury Sportjet- probably in an Alumaweld Stryker. As touched on above in much the same way as inboard and sterndriveoutboard propeller drives jet drives broadly come in two distinct flavours. Outboard jet drives whether in the form of a converted outboard or an off the shelf model are the most popular choice and indeed if you wish to experiment with a jet opting for a conversion to the lower unit.
The sterndrive unexpectedly given that its power advantage over the outboard at the propeller shaft is only 27bhp or 8 considerably outpaces the outboard and the other two options. The power difference suggests that the sterndrive should have a speed advantage over the outboard of less than 4 rather than the measured 22. The jet pump housings typicaly coverfit a range of rated prop HP per outboardmanufacturer and are then fitted with an impeller designed operate within the rated HP range example.
A jet pump housing that fits a 50HP powerhead may work up to 70HP-the difference is the liner and the diameter and pitch of the impeller fitted to the housing and HP. Get the regular outboard and then get the jetfoot attachment that way you can switch it out when you want to run a prop. I own an inflatable boat designed for a 25hp Jet I can run Alaskan rivers with 2 inches of water with that jet combo.
I also take my inflatable out into the Bearing Sea Halibut fishing when I do this I take the Jet foot off and put the prop lower unit. We dont have a good explanation for this beyond the fact that the sterndrive boat weighs 600 pounds more than the outboard and the jet drive system is less efficient than the outboards propeller. Also while the jets appendage drag is less since no gear case is being dragged through the water this may result in increased wetted surface of the hull since it.
All groups and messages. It seems that the value of what we get with a jet is great. The performance of a 360hp prop boat over jet is quite the difference too.
So value is all in what you value. The efficiency of a jet is far poorer than a prop. The safety and space savings of the jet out weigh that for me.
Each owners values are different. One drive setup propeller gear ratio etc usually cannot achieve maximum performance across the full range of speeds in a specific boat. If top speed is your ultimate priority you may want to consider an outboard or IO drive system because there are very limited choices in water jets for top speed.
The main difference between prop and jet rigging is jet outboards need to be mounted about six inches higher so owners who want to shift back and forth from prop to jet need a jackplate. The front of the jets intake grill needs to be slightly higher than the hull bottom so its leading edge cant snag anything which could damage it. Jet drives are hard to maintain and extra expensive to work on.
The impeller sucks everything up and also you cannot steer even the slightest without decent throttle so maneuvering Can be tricky in a pinch. Usually jet drive boats are lighter than outboards so handling chop can be a little rockier. The big difference between a Jet Boat and traditional Stern Drive or Outboard powered boat is that there is not an external propeller on a Jet Boat.
Chaparral for example has done some significant things to reduce noise in their jet boats and it has worked wonderfully. In 2018 most jet boats range in size from 16-24. Jet Boats vs Prop Drive A jet boat thats NOT an outboard has another issue.
The drive is always submerged in water. Marine growth can be a real problem with that. An outboard can obviously be tilted out of the water and an inboard is designed to stay in the water.
I guess if one only trailers a boat or keeps it on a lift a jet could be nice. The most interesting comparison is that between the outboard jet and the propeller. At 20 knots the former has a theoretical efficiency of 65 against 52 of the propeller.
But it is between 35 and 40 knots that the gap widens. The efficiency of the propeller decays while that of the outboard water jet stabilizes according to mathematical models above 80. You lose 13 of the power compared to a prop.
So a 90 jet 60 prop. Jets do not preform well in mud sand or shallow stagnant water where there is grass or weeds. Weather in gear or in neutral the jet is always sucking and will suck up weeds grass muck leaves etc.
And they will get stuck in the grate of the intake. Compared to a real v hull the Yamaha really slaps the waves. Having jet drives saved me a bunch of money and aggravation this season as I would have ripped at least 3 props off this season had I been driving an IO or ob.
Submerged trees are a real problem in the area that I use for wakeboarding. At cruising speed the outboard manages 50 mpg 25 percent better than the sterndrive and 52 percent better than the jet. We dont have a good explanation for this beyond the fact that the sterndrive boat weighs 600 pounds more than the outboard and the jet drive system is less efficient than the outboards propeller.
Jet drive crafts will run in less than 6 inches of water. To further define the term jet drive there are basically two types. An outboard jet drive and an inboard jet drive.
By far the most common jet drives are outboard jets. An outboard jet is simply a standard outboard with an aftermarket jet pump bolted to where the prop unit sits.