Power or Torque?

[LVjetboy]

Every engine has both of course, in different proportions. The car boat guys continue to wonder...and debate. Which engine property is more important to performance? Or are they the same thing?
I'm wondering what you guys think?
jer

[STV_Keith]

Torque = acceleration.
HP = Top speed.

[HavasuDreamin']

STV Keith is right. I will add that it depends on the boat though. For O/B applications where the boat is real light (Mirage, STV, etc.) you really don't need that much torque, thus a 2.5L motor is just fine. However, if you run a 21' Daytona or similar (heavier boat), you need a 300X or so to get that sucka out of the hole and up to speed.

[Jet Hydro]

OMG here we go again...lol...
HP = Torque
You`v got to make HP to get the motor make Torque!
The more HP the more Torque.

[Kim Hanson]

Jet Hydro:
OMG here we go again...lol...
HP = Torque
You`v got to make HP to get the motor make Torque!
The more HP the more Torque. I agree with you, no horsepower..no torque...horsepower= speed...forgetting props also boys............( . )( . )......... :D wink :p

[Jet Hydro]

I may be wrong in my thinking here but, I always want the biggest HP motor I can build because HP makes the Torque that it takes to start spinning my impeller. Once it`s spinning HP keep`s it going!

[Jet Hydro]

Oh and "NO" they are "NOT" The same thing!
If you try to twist something your using Torque to get it started. After it`s spinning it dosnt take much to move it so the Torque factor drops off. If you want to spin something bigger it takes more HP to make more Torque to start it . So the way I see it HP makes Torque and if you need more Torque, you`ll have to find more HP to make it!
If you try to slow or stop some thing from spinning by applying force your using HP to keep it spinning thus HP keep`s it spinning once the Torque got it moving in the first place.
Torque = The Hole Shot
HP = Speed or the ability to keep something moving
[ June 11, 2003, 09:14 PM: Message edited by: Jet Hydro ]

[Forkin' Crazy]

Jet Hydro:
OMG here we go again...lol...
HP = Torque
You`v got to make HP to get the motor make Torque!
The more HP the more Torque. Not always so. The engine in my truck is rated at 260hp and over 600ftlb of torque.
RPMs have a lot to do with the torque curve. Raising port heights and large camshaft profiles move this curve upward.
Bore and stroke are in the equation also.

[sorry dog]

HP = Torque the last part of this equation was left off:
HP = Torque*RPM/5252 (Also notice that at 5252 rpms torque and HP will always be the same)
Your prop or impeller don't care how much HP you got. It only responds to torque. You can have 200 ft lbs motor spinning at 5000 rpm through a 2:1 gearcase or a 100ft lbs motor spinning at 10000 rpm through a 1:1 case - The prop is gonna get the same amount of power.
The only thing HP is- is a measure of the rate work is done.
The kind of torque put out by an F1 motor ain't any different than the torque put out by a v-16 diesel. The difference here is at what engine speeds these motors make the bulk of their torque and how durable they are while doing it. The HP number just allows us judge the rate it is being applied so we can compare how much work an engine is capable of doing.

[Tom Brown]

Dog,
You got me thinking about the torque an F1 engine spanks out.
Let's see... about 900 horsepower at roughly 18500 RPM... some simple math... and we get just over 250 foot pounds of torque.
As I recall, a contemporary F1 car can do zero to 180 kph in about four seconds. That's not bad for a low torque, high horsepower setup. Maybe there's something to what you're saying...
Also as I recall, an F1 car can turn right. :D
[ June 12, 2003, 11:28 AM: Message edited by: Tom Brown ]

[Hal]

Put that same motor in a 4000 lb car and the high horsepower low torque motor would,nt get out of its own way... :confused: :D

[Essex502]

Guys...horsepower is simply the result of the calculation of torque at a particular RPM. Horsepower is a measure of work done based upon, in this case, rotary motion. Torque and horsepower can be equal at 5252 RPM ONLY if the motor can spin to that rpm. In the case of diesel engines that are high torque at low RPM's they may not be able to get up to 5252 RPM.
Small motors like F1 build peak torque at very high RPM and have transmissions that keep the RPM in the desired range.

[mickeyfinn]

Here is my .02:
HP is just the measure of how much work the engine is capable of doing. The rpm does not enter the equation of HP except that you have to pick at what rpm you measure it. When assembling and selecting components for the engine you have to choose where you want to make that horsepower. If you make good power on the bottom end you will produce more torque from, make the power on the top end less torque. Once you have assembled the engine you can then change the props, gears, impellers etc to make changes which will alter where on the curve the boat actually sees the torque.
Seems to me that if you build for decent torque all the way through the rpm with max torque at max rpm you get the most flexibility with making changes with the props, etc.
The 5252 number means absolutely nothing. It is a coincidence which happens on a large number of boats. I saw a thread a while back which made an absolutely true statement, Covert to metric units and the 5252 number doesn't work anymore.

[Jrocket]

You guys think too much about it... :D

[You Te]

So where are the photos of the DCB Jrocket?
Hey, happy fathers day to you.
You Te

[sorry dog]

You guys think too much about it... I agree, but for us outboard folks, like the Honda commercial: if you don't have to worry about your motor, what will you think about...
BTW- The 5252 # maybe trivial but not meaningless. Often power numbers are given without an " at #### rpm" or not given with a torque number. Knowing that at 5252 rpm they are the same, give you a point to approximate from to fill in blank.
I'm sure there is also a similiar point in metric terms where the same is true.

[Infomaniac]

bump for first page of archive

[Boat Racer]

STV Keith is right. I will add that it depends on the boat though. For O/B applications where the boat is real light (Mirage, STV, etc.) you really don't need that much torque, thus a 2.5L motor is just fine. However, if you run a 21' Daytona or similar (heavier boat), you need a 300X or so to get that sucka out of the hole and up to speed.
On the same 21' boat, I'd put my money on a 2.5 280 over a 300X anyday!!!

[Tom Brown]

It's going to be a terrible loss when we loose access to this thread.

[sorry dog]

Wow, this shit is old...