posted 11-26-2002 11:17 AM ET (US)            

(Now a broken link)

Among other things, it says outboards are to be rated at the prop shaft and that rated horsepower is to be within +/-10% of measured horsepower

posted 11-27-2002 09:04 AM ET (US)            

Ten percent does seem like a large range. I wonder with all of the newer manufacturing equipment available if the manufactuers couldn't limit the range. I don't think I'd mind +/- ten percent on a 5HP outboard. It doesn't seem reasonable to have such a large variation on say 100HP.

posted 12-01-2002 12:29 PM ET (US)            

But this flies in the face of the +/- 10% margin we have always heard about. In fact, Evinrude's own web site plainly states that their 200 hp motor puts out nearly 220 hp! (which, by the way, makes Sal DiMercurio's 200 Evinrude Ficht pretty much run-of-the-mill if it dyno'ed at only 212 hp.)

posted 11-04-2003 06:32 PM ET (US)            

(I added to this old thread because I thought the comments on the old thread are relevant)

I just read the thread on the release of the E-Tech engine from Evinrude and went to the web site to see if how the horsepower ratings were determined. All I could find is that the ratings comply with the ICOMIA 28/83 standards. Went to ICOMIA and could not locate the standards, other than that the power is measured at the prop shaft.

I recently read a magazine review of a boat-motor combo and saw that the horsepower was rated using M - HP never seeing M-HP before I read the article carefully and found M-HP (Metric Horsepower) which is less than B-HP (Brake Horsepower). The reviewer stated that many motor builders from overseas like to use the M-HP because they can advertise a bigger HP number.

My question is dose the ICOMIA 28/83 standards specify Metric or Brake Horsepower?

Could the differences in performance that some members are experiencing be caused by some companies are using brake horsepower and a competitor is using metric horsepower?

posted 11-04-2003 07:12 PM ET (US)         

I know of a situation where an owner of a 1991 200HP Yamaha was told, by a Yamaha mechanic who also had experience with other brands, that the engine really only puts out about 175 HP. Having paid a high price for 200 horses, he was not too happy. The reliability of that engine, with I think about 500 hours on it, however, has been excellent.

Conversely, I have been told that my 1997 Merc 200 EFI's are really putting out more than 200HP each. In racing versions, Mercury gets 260HP out of these. The 225 Mercury EFI has been indicated at more like 240 HP, and the same block is good for the 300HP version.

It's been no secret that Mercury's rise to fame in the outboard market was partly based on deliberate under-rating of HP. One of their really early engines was a little green painted 10 horse model, that would walk away from an OMC 10.
But in reality, Mercury knew the little engine was putting out more like 20 HP, still selling it as 10. I have suspected for the last 30 years, that some of this philosophy still exists. I know it did with the now-classic in-line 4's and 6's.

posted 11-04-2003 07:55 PM ET (US)            

On the Evinurde site the 135 DI is rated for 107 kw , 135 x 746=100,710 are the Evinrude engines producing more power than advertised?

Suzuki 140 producing 103 kw while the “lessor” Evinrude 135 puts out 107 kw

Hummmmmmmmmmm

posted 11-04-2003 08:27 PM ET (US)            

What I am trying to find out is that 10% based upon Brake HP or Metric HP. If one manufacture uses the metric standard then when we see an hp rating we are not buying the power that we think we are.

I thought that the 10% spread was for taking an engine off the line and testing it for actual power produced. So some engines pulled from the line (rated for 135 hp) could produce as few as 121 hp or as much as 148 hp and still be within specs. not for advertising purposes i.e. knowingly producing an engine that will give only 121 hp and putting a 135 hp sticker on it.

posted 11-04-2003 11:31 PM ET (US)            

Dgp, now I am really confused…

Say goodnight Gracie,

posted 11-05-2003 09:49 AM ET (US)            

In english: A motor designed to produce 150 hp can produce between 135 hp and 165 hp. But, one motor will not produce 135 and the next 165. If this was the case, the company has design, supplier, or manufacturing problems and their costs will increase substantially. But, they will try to produce motors in the range from 145 to 155. This will allow them to make adjustements to their production before an issue becomes a problem. What trending means is that, instead of 150 hp being the nominal, 155 becomes the nominal. The range of "in control" production then might become from 150 to 160. Trending is extremely common in manufacturing. Unfortunately, one month may be trended on the high end and the next might be trended on the low end. There are a lot of variables to include to determine where the trend is...This helps explain why one person's boat does not perform the same as another's that is similarly equipped.

posted 11-05-2003 02:16 PM ET (US)            

I wonder why the OB manufacturers never rated torque????
Pretty important when moving a boat with load on it all the time or pulling a skier.

posted 11-05-2003 03:01 PM ET (US)         

So this would support the manufacturing tolerance discussion.

My only point with all of this is that outboards ARE priced by the HP (within a given technology), so manufacturing tolerances aside, I think it is unethical and deceptive business practice to use this 10% or 5% factor on the low side. On the high side, there is no loss to the consumer, and the buyer is assured he is AT LEAST getting what he paid his money for. If someone is selling a 140hp engine, it darn well should be faster top end than the other guy's 135. Technologies and gearing can make a difference in
acceleration, but for top end, where HP is HP, the differences should be proportional to HP output.

posted 11-06-2003 10:59 AM ET (US)         

Are the dynamics of torque the same in water as they are on land? It seems the RPM of the propeller turning through the water is what moves the boat. The loads seem to be a constant until you reach planning speed, then they reduce. Therefore, you only have two variables in load. (I know this is an over simplification)

If this is incorrect, then the prop would be slowing down due to load and the lack of torque, whereby the prop would not be turning the RPM indicated. It seems if the engine horsepower is large enough to turn the prop at the desired RPM, then the hull will react accordingly, regardless of one engine's torque versus another.

Ex: Two 150HP engines of different brand turning the same prop on the same hull, turning the same RPM will move the hull identically. They're power band may be different, but the resulting force on the hull should be the same. Is this all wet?

posted 11-06-2003 11:10 AM ET (US)            

Changes coming for horsepower, torque numbers
By AP

Car owners may soon gain more confidence in the horsepower that automakers claim for their vehicles.

A group of engineers is developing a new standard to verify automakers' claims for the power their engines develop.

In the recent past, automakers from Jaguar to Hyundai have admitted they advertised unrealistically high output numbers for their cars.

"Horsepower numbers are absolutely important to our readers," said Frank Markus, technical director of Car and Driver magazine. "It's one of the most crucial numbers. It's how we tell them why one car is better than another."

The Society of Automotive Engineers is revising its standard for measuring horsepower and will suggest automakers have an independent observer verify the numbers they claim for horsepower and torque, said David Landcaster, General Motors Corp. engineering group manager and chairman of the SAE committee developing the new standard.

One horsepower is the amount of force necessary to lift 550 pounds 1 foot in 1 second. SAE has developed standards for everything from motor oil to vehicle electronics.

The new standard will also set a procedure for how to test torque, the other main force automakers advertise.

Torque measures the turning force generated at the wheels. While high horsepower numbers generally equate to higher top speeds, torque determines a vehicle's acceleration and ability to pull heavy loads.

"Companies have always been able to claim whatever horsepower they wanted," Markus said. "Adding some accountability for the numbers would be a good thing."

Car and Driver caught Jaguar claiming 10 more horsepower than its high-performance S-type R model actually developed a couple of years ago. The automaker then revealed it used a test procedure that gave it higher numbers than what is generally accepted by engineers.

Automakers can test for horsepower and torque in a variety of ways ranging from testing an engine sitting on a bench to evaluating the actual power transmitted to a vehicle's wheels.

Ford and Mazda have also had to lower the horsepower they claimed some of their cars produced.

"It makes you suspicious when a car claims more horsepower but has less performance," Markus said. "Some companies go with the number they like, especially when it gives them a nice round number like 400 horsepower."

The current test, which was last revised in 1970, allows automakers to claim horsepower and torque figures higher than what most owners will actually experience, Landcaster said.

Ford, GM and DaimlerChrysler support the idea of a new independently verified horsepower test.

posted 11-06-2003 11:57 AM ET (US)            

What determines torque in an engine is the piston diameter (bore), the compression ratio, and the length the piston moves (stroke). The larger the bore or the higher the compression, the greater the force that is exerted on the piston after combustion. (Force = Pressure*Area). The longer the piston moves, the greater is the radius (stroke=2*crank radius). The bore and stroke also make up the volume of the engine (cubic inches). Now, take the forces that are exerted on the piston and factor in the rpm and you essentially get the engine horsepower. Of course, there are inefficiencies throughout the engine and the drivetrain (lower unit and prop for boats) that will rob the engine of horsepower. Prop slip is a major factor in robbing "horsepower" from a boat.

For the boat, the drag force on the hull is proportional to the speed of the boat both above and below planing speeds. The drag is related to the area of the wetted surface of the hull (unlike friction) basically because more water is displaced by the larger "contact patch", hence why trimming the motor also increases speed. The motor most supply enough force to overcome the drag force at a given speed to accelerate the boat to a higher speed. It is also not a linear relationship and I don't know off-hand what exactly the relationship is.

What does this mean? Two engines, pushing identical boats, using identical props, will differ in speed based on the inefficiencies in the engines and the wetted surfaces of the boats. Thus, if one motor weighs more than the other, the boat will sit lower in the water and will go a little slower...albeit not much.