lb's of thrust

[edjr]

anyone know haw many lb's of thrust a 92 suzuki dt 140 puts out

 

[JB]

Re: lb's of thrust

Depends on the prop.

 

[edjr]

Re: lb's of thrust

do you think it can be over 7000 regardless of prop, im thinking about putting a new tilt and trim but its only rated for 130 hp but is rated for 7800 of thrust?

 

[Dave Abrahamson]

Re: lb's of thrust

7800 LBS of thrust?? supersonic Suzuki!<br />An Air Force F84F has one Wright 765-W-3 turbojet, 7,800 lbs. thrust<br />A Cessna CJ2 has a Williams’ FJ44-3A-24 dual-channel FADEC engine, 2400 lbs of thrust.<br />I think the 7800lbs refers to the thrust of the hydraulic power of the T&T unit.<br /> <br /><br />Dave

 

[Drowned Rat]

Re: lb's of thrust

edjr. HP and thrust do not equate without a high degree of inaccuracy. However, 1 hp is roughly equivalent to 70lbs. thrust at best. So, your motor running at peak performance propped for maximum thrust theoretically is capable of 9800 lbs of thrust. When you factor the age of the motor, prop slippage, and various other power robbing elements, you are more likely closer to 7000 lbs. on the low end and 8400 lbs. on the high end. Hope this helps.

 

[Drowned Rat]

Re: lb's of thrust

As Dave points out. Pounds of thrust in the air and in the water are vastly different.

 

[edjr]

Re: lb's of thrust

do you think it would be alright to put the cmc pt130 on this motor

 

[Paul Moir]

Re: lb's of thrust

DR - I think the 70lbs vs 1hp comes from trolling motor comparisons. The trolling motors have very high thrust props that you don't see on outboards so they can move heavy craft with their weeny motors.<br /><br />Anyway, real life speed propellers produce a lot less thrust. It's a bit of a wild guess, but I would think about 1000lbs hull resistance at full speed would be in the ballpark.<br /><br />Another way to look at it, do you really think you could park 3 midsized cars on your transom? Or howabout this one - that the engine could completely lift two boats out of the water, straight up?<br /><br />To answer edjr's question though - why not ask CMC? I see it's rated for 130, they might just say it's fine for the DT140. The way I've seen it, what really matters is the weight bouncing around on the transom rather than the thrust. But ask the people who designed it.

 

[Drowned Rat]

Re: lb's of thrust

Good point Paul. Assuming 1 hp equals about 750watts. 140 hp equals 105 kwatts. Thats alot of power. Theoretically the motor should be able to "lift" 33,000 lbs. 1 foot per minute per hp. Or 3,300 lbs. 10 feet per minute per hp. For a 140 hp motor that's a stagering number. The limitation is in the prop I think, not the motor. Yes, the prop slips in the water, but the thrust is still there no? Hmmm. Interesting experiment.

 

[edjr]

Re: lb's of thrust

i called cmc and they said it will work on that motor and the only thing ishould be concerned about is trimming it all the way up at wot ( i dont know who does that anyway) and be sure i use a transome saver. thanks for all your input

 

[Dave Abrahamson]

Re: lb's of thrust

If you have 8-9000 thousand pounds of thrust on the transom of a 2500 pound boat, shouldn't you theoretically be able to achieve mach 1+? <br />I know an unloaded 40,000 lb F-15 will go supersonic STRAIGHT UP/VERTICAL with two 25,000 lb thrust engines. (How much thrust do you suppose Miss Budweiser puts out?)

 

[edjr]

Re: lb's of thrust

cmc said the thrust rating is for the hydro's if you have that much hp pushing against the ram it could blow out the hardware the holds the ram to the unit. i truly dont know what the thrust would be pushing against the trim unit