Fudge factor in stated horsepower ?

[chris andrews]

O.K, I posted on here a while ago that I was looking at the Suzi df140. I'm ready to take the plunge, but I was talking to a guy who told me that the stated h.p was not the actual h.p. According to him, that df140 is only about a 130 or even less. I've often wondered about this before with outboards in general. I've seen the opposite as well, with actual h.p being greater than stated h.p. Some engines of the same h.p will run stronger/weaker than the other. Is this due to torque differences, or max h.p output at different rpm's? ( theoretically the linear curve) Is there a standard that manufacturers must abide by in stating an engines h.p rating?

 

[JB]

Re: Fudge factor in stated horsepower ?

Yes, Basscatter, there is a standard. Stated HP must be within 10% of actual. The DF140 is, therefore, somewhere between 126 and 154 at the rated rpm, and the actual may vary from one engine to another. The same applies to any other outboard rated at 140HP.<br /><br />Differences in performance of engines rated the same HP are because of differences in torque curves.<br /><br />Remember this about outboards: Horsepower sells it, but torque makes it go.<br /><br />(243)

 

[seahorse5]

Re: Fudge factor in stated horsepower ?

One way to find the actual hp a motor produces, is to read the EPA emission reports as the rated power is listed in KW/Hrs., convert that to horsepower and you have what hp the motor is certified at. That will be the actual hp and not the advertised hp.<br /><br /> http://www.epa.gov/otaq/certdata.htm#marinesi <br /><br />KW/Hr. X 1.341 = HP

 

[chris andrews]

Re: Fudge factor in stated horsepower ?

Well I guess I should ask if any of you guys know if this engine is a relativley strong or weak performer for a 140, per the rating ? I'm replacing an old 84' Johnson GT150. The boat is only 17' 01''and 980 lbs. ( basscat Caracal) The performance was awsome. Makes me a little nervous that I might only be getting as low as 126 h.p. But I sure like that engine...

 

[JB]

Re: Fudge factor in stated horsepower ?

Haven't run a DF140, basscatter, but I had a DF70 that would stay with a Merc 90 on identical boats.<br /><br />I would have no reservations about replacing a '84 Johnny 150 (rated at the flywheel) with a DF140 (rated at the prop). You may very well have only 130-135 at the prop already, and that is if the Johnny is in perfect tune.<br /><br />Those Suzis are really wonderful engines.<br /><br />(230)

 

[chris andrews]

Re: Fudge factor in stated horsepower ?

JB, thanks for the insight. I guess I was waiting for someone with lots of boating experience to ease my nerves about that issue. I'm going to pull the trigger on that motor this week. I'll let you know how she does. Thanks again !

 

[walleyehed]

Re: Fudge factor in stated horsepower ?

The DF140 is a good, strong engine.<br />The '84 GT150 has the same block and port timing of the 200 of that era.<br />I don't think you will lose or gain much speed-wise, but the fuel economy will impress you greatly.

 

[Texasmark]

Re: Fudge factor in stated horsepower ?

And on fuel, Kenny, Suz's were loopers and the Johnny was only crossflow at that time....right?<br /><br />That being the case, I agree on the impressive fuel economy...Even the direct charged inline 6 merc I had was a tremendous improvement over the OMC crossflow.<br /><br />Mark

 

[gss036]

Re: Fudge factor in stated horsepower ?

How much of a weight difference is there between the 2 motors? Some of the 4 strokers are pretty heavy and you only have a 17 ft boat. Make sure you can handle the weight. I agree with everyone that Suzuki is a good motor.

 

[JB]

Re: Fudge factor in stated horsepower ?

I think the weight is pretty close, GSS. The Suzi DF140 weighs about 412lb. The Johnny looper 150 weighs around 380lb and I think the crossflow was heavier than that.