Does anyone have Full HP and Torque Info on outboards over 150 HP

[4JawChuck]

Re: Does anyone have Full HP and Torque Info on outboards over 150 HP

No problem Hwsii, I like the fact you are taking a scientific approach to learning...trust me not everyone does.

What I see is a lot of people coming to me asking "I want my engine to put out XXX amount of HP" without looking at their application to decide how best to approach the performance they desire.

I could easily build them a 2.0L turbo motor that put out 400HP but if that engine was going into a 3/4 ton truck the thing probably couldn't get out of it own way and would perform poorly in every aspect even if their torque area under the curve were equal to a larger engine putting out the same amount of HP. Obviously a large displacement motor turning a lower RPM is a better fit for the usage pattern although there would a loss of mileage at low rpm in comparison to a small turbo motor.

You could have two engines both producing the exact same HP but not perform at all the same because their torque curves do not match the load, in fact most people find torque production is far more important and usable in the real world and gives the kind of performance you can feel in the seat of your pants and on the stopwatch or speedo.

I know a guy who swapped out his 200 HP 1991 Merc for a newer 225HP Yamaha and was perplexed that he never gained any speed and actually found less performance throughout the operating range, he thought there was something wrong with the motor. After checking out the new motor for running condition (it was excellent) the problem was the older Merc was 3.5L in displacement compared to his Yamaha which was 3.3L in displacement and the old Merc was under rated from the factory making it perform close to what a 225 HP motor would accomplish. He was sorry he didn't just freshen up his old Merc and save the hassle of spending a bunch of money on a newer motor expecting better performance from less displacement.

The good part was I bought his old Merc knowing full well what makes a boat move through the water and after a set of rings it performs far better than that newer Yamaha could ever hope to achieve. In closing HP ratings are only one part of a complex equation when it comes to performance, don't be fooled by the numbers on the hood...its what's under the torque curve that counts.

 

[hwsiii]

Re: Does anyone have Full HP and Torque Info on outboards over 150 HP

Chuck, I am definitely learning from the charts and your knowledge.
For many years I worked for a company that did cleanup after fires, floods and chemical spills, all over the world, so I have traveled a lot. My position in the company was as a Senior project manager and Hi-Tech project manager. I ran most of the projects that required cleaning of main frame computers and hi-tech machinery. My knowledge of chemials was a help in my position as well as my computer hardware knowledge. We did a cleanup for the Seagate hard drive plant in Singapore, and I established the criteria for the cleaning procedures required to clean the machines that made the platens for their hard drives. They were not going to clean the machines because they were scared of the ramifications of producing bad hard drives and them losing their reputation in the business. But then they found out that the lead time to replace their equipment was going to be over four months and they might lose most of their market share not having enough units to keep their sales up, so they ended up HAVING to let us clean them. LOL
Did you know in a fire in a manufacturing plant that there is hydrochloric acid produced from the burning of plastics and sulfuric acid produced from the burning of wood, and when it invades high tech machinery it actually starts eating away at the circuits on the circuit boards as well as all of the metals. A Panasonic facility in Georgia had a heater in a freon cleaning tank for the circuit boards run away and just created a cloud in the plant, NO fire. But the chlorides from the freon physically stopped the assembly lines from running in less than two weeks because of the corrosion created from the chloride becoming Hydrochloric acid and creating the corrosion. Enough of that, let's get back to what we were discussiing, as I get older I reflect back on the past. LOL

I was thinking that I also have a full HP chart for a 4 stroke Yamaha 150 that was included with evinrudes comparison of the two motors, and we might compare the HP and Torque curves of these two motors and see what they are.

I will do an analysis and the charts and we can compare them, if you don't mind.


H

 

[4JawChuck]

Re: Does anyone have Full HP and Torque Info on outboards over 150 HP

I don't think this discussion would be complete without comparing two strokes to four strokes, besides the obvious weight penalty of running a four stroke many people think a 200Hp four stroke should perform the same as a 200HP two stroke.

Nothing could be further than the truth as anyone who has repowered with a four stroke will tell you. Two strokes typically produce higher torque in the midrange and it 'humps" up higher before the HP peak giving a lot more punch once your moving. A four stroke may produce more torque just off idle but the advantage quickly falls away as rpm rises into the midrange. A four stroke torque profile is usually much flatter and falls away less as rpm rises where a two stroke torque profile rises quickly and falls off towards the HP peak.

In essence a four stroke just feels slow in comparison because of its torque curve profile, the HP rating may be the same but there is no comparison in running characteristics. This is another reason why the HP ratings is of little value when comparing prime movers to each other, I have seen first hand smaller HP rated two strokes out perform larger HP rated four strokes in every aspect including top speed. Unless your boat is exceptionally heavy a two stroke will outperform a four stroke every time because of its torque profile.

The only exception is in the off idle performance where a four stroke has a significant advantage, if you plotted the torque curve of a four stroke and a two stroke you would see why...the torque is usually nearly double at rpms below 2000 with a four stroke typically. Just another example of where HP ratings have nothing to do with real world performance.

Of course we haven't even touched on fuel efficiency where the four stroke has an advantage below the peak operating rpm, the closer you get to the HP peak the less advantage it has because of crossing lines of efficiency and rotational losses. Thats not to say much of a four strokes disadvantages can be eliminated or reduced with charge tuning such as seen in the SHO Yamahas, but then imagine what could be accomplished with a tuned pipe on a two stroke on the water.

It is unfortunate the technology/development has stalled on two stroke marine engines since there was so much to be gained with tune pipes even if the packaging would be complicated and heavy. Imagine what a 3.5L two stroke with tuned pipes would put out with tuned pipes, since marine race motors of this size put out 400HP I imagine 600Hp is not out of reach and an unbelievable torque hump in the midrange that would triple what any four stroke could achieve is not out of the question equipped with tuned pipes... even if the pipes themselves would be larger than the motor. Then add boost valves and variable staged turbo charging...

 

[hwsiii]

Re: Does anyone have Full HP and Torque Info on outboards over 150 HP

Chuck, I keep going bak to Yamaha's site to find even one boat that is using the 150 4 stroke, and every time I keep getting an internal error from their server, as soon as I can get some numbers to run with that motor I will post them.


H