best of the best outboards

[juggernaut]

Simply put, torque x revs = hp.

So for example one motor with say 200nm and another with 300nm at the same revs, the second motor will have more hp at that rpm. This is also why rotaries make decent hp through revs. They had to rev to make hp because they had so little torque.

You will generally find 4 strokes have to rev higher to make peak hp compared to a 2 stroke making the same hp. This is because they generally develop less torque than a 2 stroke.

[Lovey80]

Horsepower = Torque (lb-ft) X RPM Divided by 5252

1 horsepower = 33000 foot pounds per minute.

[Noelm]

Which is why lots of manufacturers reluctantly advertise HP at X RPM, some might have a tiny bit of fine print buried in a spec brochure that goes something like "90 HP @ 5,500 RPM" so, unless the torque is really something to be proud of, they just tell you the HP, or maybe the torque, but just skip the RPM range where everything happens.

[STUIE63]

So what you guys are saying is that the torque curve should follow the hp curve. Have I got this right.

[juggernaut]

So what you guys are saying is that the torque curve should follow the hp curve. Have I got this right.

No that's not quite right. Hp follows a combination of torque and rpm. What you say is broadly true up to the point of peak torque in the rpm range. After the point that peak torque is reached in middling rpm, the torque curve will start to diminish. If the rpm are sufficient to cancel out the rate of diminishing torque after peak torque is reached, you Keep making hp. But when the torque diminishes at an increasinga rate further up the rev range, hp also starts to drop off. At this point there is no point in revving the motor harder because the torque has diminished past the point of sustaining further hp increases.

[Lovey80]

I didn't thinkTorque ever turned negative but rather flatten out. I thought that is where the " red line " point is often measured.

[up the creek]

obviously a 2hp motor doesnt make much torque but a 40 hp makes some torque and a 200hp makes a lot of torque im not saying its related in every way but obviously more hp more torque

[Noelm]

You didn't understand what was written, HP, Torque and RPM are all tied together, so a 2 HP motor still has HP and RPM, so the relationship (torque curve) is relevant.

[STUIE63]

Then how does a formula that involves revs and hp = torque work
i have seen dirrerent dyno sheets that say some hp = x torque and the same hp = x times 2 torque
as in diesel motors versus petrol motors. Hence my comment earlier that they should give torque curves not hp ratings for outboards. Because torque is usable power and hp is bragging rights

[TheRealPoMo]

Not sure about your dyno sheets with the 2 times thing.
I dimly remember from mech engineering lectures that the proper formula was kw=Nm x angular velocity in radians per second...that was 30 years ago though...the constant someone mentioned earlier must make the conversion more simply.
With your diesel, peak torque would be at low rpm and would fall off quickly after that. The increasing rpm as a multiplier would lose its effect the more the torque falls off. Multivalve 4 stroke petrol engines keep this multiplier going alot longer because of increased operating rpm and the fact the peak torque is made at higher rpm than diesels. VVT on petrol engines and technology in modern diesels bring them closer together
Hope this makes sense. Have the flu bad so probably gibberish. ..

[gofishin]

Simply put, torque x revs = hp...

Horsepower = Torque (lb-ft) X RPM Divided by 5252...

In S.I. units, yes, Power [kW] = Torque [N.m] x 'rotational speed' [radians per second]... but who uses these units in Aussy everyday life?

Including appropriate unit conversions, the formula becomes:

Power [HP] = Torque [N.m] x 'rotational speed' [rpm] / 7124

... which will be a lot more useful gents.

... You will generally find 4 strokes have to rev higher to make peak hp compared to a 2 stroke making the same hp. This is because they generally develop less torque than a 2 stroke.

Comparing equivalent displacements, generally true when looking at peak torque. However... an equivalent displacement 4 stroke will generally produce peak torque at a lower speed, albeit a lesser peak, and nearly always will provide a flatter torque curve.

In addition, a peaky torque curve provides a less 'user friendly' offshore fishing motor than a 4 stroke. The 2/ will give you that wham-bam power band effect... but this is exactly why you will read thousands of comments/articles/Ausfish Posts!! etc where experienced people will say you are always on & off the throttle with a 2/, but not so with a 4/.

Pity that torque curves in the OB industry are such a secret.

Popcorn time!!??

Oh, and here is some comparison data for you, extracted from the US EPA website. They give you both max HP at the relevant speed for this max HP, and max Torque, again with the relevant speed.

Using the above equation (but rearranging it), you can work out the corresponding Torque and HP - as per the green columns in the attached.

Cheers
Brendon

PS. This data obviously has a few years on it, and is obviously Gen1 E-TEC's. Haven't looked up or downloaded newer US EPA data for years.

PSS. I am not an E-TEC basher, just don't like their typical 'spin-doctor' BS marketing they used to use. I previously used this 'real' US EPA published data to show that a previously 'E-TEC' published torque curve comparison was created with a lot of 'artistic licence'!
I appreciate the advancements in technology they have included in their Gen2 donks, and look forward to more independent tests/comparisons/data being released. This can only be good for the industry!

[Noelm]

Regardless of formulae, theories or anything else, the above is 100% true, with a 2 stroke (less so with DFI or HPDI) you are almost constantly on and off the throttle, been there, and done that for decades.

[Andy56]

I get a sense of dejavue talking about torque and what not. As far as I know, the outboard association decided ages ago all power measurements were to be done in a particular way so we could compare apples with apples.
We have had tug of war tests, power tests of all persuasions and etec win every time. If it wasn't true, we would have other manufactures joining in and pulling etecs under. Which I haven't seen. So there must be some truth to their claims.
Face the facts guys, Etec gen2 have leapfrogged everyone. And we should all be happy because it will force the others to up their game.
Isn't that what we want?
Or are we all just happy to get the cheapest last century tech? There will always be people who buy holdens and fords but there are also many people who will buy BMWs and MERcs etc.And all the technology in BMWs and MERCs has filtered down to holdens and fords.
We should rejoice that they have pushed the bar higher is what I am saying. Neither of us may buy one, but that shouldn't affect respect.

[Spaniard_King]

in those cases my tohatsu 18hp with a 3 year waranty aint so bad even if i paid a little more then a 15hp merc jap super..

Pray you never need to use that warranty, ever herd the term blood from a stone!!

[Noelm]

I still don't get where or how e-tec has such a technological advantage, or is such a leap forward, it is simply a refinement of what they had, the same basic power plant, good or bad?? who cares, you want one, you buy one, you want an old carby motor, but one while you can, you want a step back in time 4 stroke, buy a Mercury, want the best warranty in the game, buy a Honda, want a reliable motor, buy any one of them, pretty simple really.