Jet drive Pull or Push????

Thread: Jet drive Pull or Push????

1. Jet drive Pull or Push????

i remember some thread on hot boat about the discusion of jet drives making the boat go foward by the force of sucking or pushing the water. Lets hear your thoughts!

2.

3. the jet doesn't suck itself along it may have suction at 0 mph, but as soon as the boat is moving, there's positive pressure in the intake, which means the sux theory can sux it

4. yeah maybe i should have worded the question a little better, i hate things that suck

5.

6. Its all thrust. If it were suction, in theory we would suck the boats underwater.

7. go by your local f.d. and ask them if you can have ahold of one of their 2 1/2" nozzles, and ask them to open it up wide. then you'll figure out what thrust, or "nozzle reaction" is all about. and thats putting out nowhere near the amount of water that a jet is

8. Originally Posted by Wet Dream
Its all thrust. If it were suction, in theory we would suck the boats underwater.

ok, maybe stupid question then, or i just dont realize something simple here......when we ride with the diverter all the way up and the nozzle spray is going up in the air........wait a min i think i just figured it out...like jets4fun said, i guess if i strapped on a pair of roller skates and opened up that fire hose, i would be zinged across the parking lot.......so its the motion of water passing through the nozzle creating the thrust?

9. bingo

you wouldnt need a pair of skates. in the fire service its referred to as nozzle reaction. and if you're not paying attention it will knock you on your ass

10. The short and simple;

The jet drive is a powerful, engine-driven water pump that sucks in great quantities of water through the bottom of the boat and shoots it out through a nozzle at the stern. Operating on the principle of physics that, "for every action there is an equal and opposite reaction", the boat is propelled forward.

11. All thrust!

No suction at all after you get up to speed. It just scoops it up and shoots it out once you get moving a little.

12. Originally Posted by little squirt
ok, maybe stupid question then, or i just dont realize something simple here......when we ride with the diverter all the way up and the nozzle spray is going up in the air........wait a min i think i just figured it out...like jets4fun said, i guess if i strapped on a pair of roller skates and opened up that fire hose, i would be zinged across the parking lot.......so its the motion of water passing through the nozzle creating the thrust?
So my guess is you never owned a 'stand up' Jet Ski and blasted yourself in the NADS trying to get going in deep water! Its a quick education on how a jet works. LOL!

13. Guess the short and simple wasn't Simple enough! lol

The Impeller--Like a compressor--PULLS IN water and PUSHES it out through the nozzle! Just that simple!

If it don't suck! you don't go!!---cuz, Thats how an IMPELLER Works!!

14. Originally Posted by Wet Dream
Its all thrust. If it were suction, in theory we would suck the boats underwater.
Well, not really. The boats buoyancy is greater than the suction of the pump. When under way the pressure of water being fed into the pump might be slightly greater/less what's being expelled Too much water charged at the suction housing passes under the "suction" housing and the term over stuffing the pump is at play. Either way, the forward momentum of the boat and the hulls buoyancy and ability to get on plane over comes the impellers ability to "suck the boat down". At idle in shallow water it can suck debris up from the bottom. Now if the pump by itself was to magically spin somehow by itself then it would indeed suck itself into the water...but...with the pressure of thrust exiting the other end would still move forward.
Soooo in short...yes...the pump does suck.
See, I'm not just a pretty face

15. Yea understand how a jet works as far as pulling in water and shooting it out, had a couple, just never thought of the physics part rather than mechanical part.

16. Yes and no. At idle, the impeller is replacing water that has been displaced at the nozzle. As speed increases, the impeller is not sucking, it is using and compressing water that is being forced into it.

If the impeller were sucking through the rpm range, the intake would always be at negative pressure, which its not.

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