Must read...2-stroke vs 4-stroke comparison

[seahorse5]

Re: Must read...2-stroke vs 4-stroke comparison

Forktail,<br /><br />They also had identical 22' Aquasports, one with the Evinrude FICHT and one with the F225. Both propped using factory props identically. The Evinrude was about 4 seconds faster from 0 to 30mph and top speed was about 5mph faster. The Yamaha was quieter at idle, but then the noise factor was about the same at cruise and at WOT.<br /><br />Both with this comparison, and the one with the 29 Angler, the Yamaha was rigged and propped per the factory specs. Yamaha personell even got to run the comparison and see the dyno results, from what I was told. The boat was at last years Miami Show.

 

[rons boat]

Re: Must read...2-stroke vs 4-stroke comparison

How much fuel was used by each. I am very interested in MPG comparison.

 

[Forktail]

Re: Must read...2-stroke vs 4-stroke comparison

"Both propped using factory props identically."<br /><br />What do you mean by "identically"? Same pitch? Same diameter? Or compensated for the large gear ratio difference?<br /><br />Evinrude's test of the Aquasport shows they used the 14 3/4 X 19 pitch (SST) prop. And it looks like they again used Yamaha's same 15 1/4 X 19 pitch. Calculating the speeds based on the 2:1 and 1.86:1 gear ratio difference, the Evinrude 225 will be 4.1 mph faster. Add to that the speed reduction of the Yamaha due to the bigger diameter prop and you probably get the 5 mph difference in top speed mentioned. This is just basic propping...no big news here.<br /><br />"the Yamaha was rigged and propped per the factory specs."<br /><br />What are the "factory specs" for propping the F225? And what are the "factory specs" for propping the Rude 225? Rude's test of the Aquasport/225 used the 19 pitch SST, yet their test of the Angler/225 used a 17 pitch Viper. So what's the factory spec for the Rude 225? Looks like they change props only on their outboard? You can't honestly say that propping Yamaha's F225 for twins on the Angler would be the same as propping for the single on the Aquasport.<br /><br />"The Yamaha was quieter at idle, but then the noise factor was about the same at cruise and at WOT."<br /><br />This is hard to believe, especially since Rude doesn't publish any noise data for these kinds of tests (Yamaha does). I've seen Yamaha's decibel test on the F225. 68 Db at idle, 85 Db at cruise and 95 Db at WOT....and this is for twins!.<br /><br />"Yamaha personell even got to run the comparison and see the dyno results, from what I was told."<br /><br />I understand this was observation only. No involvement by Yamaha testing engineering staff. In other words, it was not a collaboration between Rude and Yamaha to provide representative results.<br /><br />Has anyone seen the sales figures between the two? Something that shows what people really want on their boat? With Evinrude being so much better they must be selling more of them than Yamaha?

 

[seahorse5]

Re: Must read...2-stroke vs 4-stroke comparison

My mind outruns my fingers when I type and should have reviewed my post.<br /><br />The engines were propped to factory specs - 5000 to 6000 rpm operating range - and both turned identical rpms, just under 6000. Because of the differences in torque, the Yamaha used a 2:1 lower unit ratio compared to Evinrudes 1.86:1. That made a difference in prop pitch. Both motors had their respective manufacturer's prop installed. The engines were tested with stock props and at various transom heights to get the best performance. <br /><br />I don't have my notes handy, but the Evinrude was better on fuel consumption at most speeds and had fewer total emissions than the 4 stroke EFI Yamaha according to the EPA tags required by law. They were each set up just like a customer would get from a dealer. There were no trick items that would give one an advantage over another, everything was box stock.<br /><br />I am curious to see a shootout with the 250 hp models including Merc's special Optimax, and now maybe with Suzuki's 4-stroke 250 if it is available soon.

 

[fridays]

Re: Must read...2-stroke vs 4-stroke comparison

I'm with forktail. Run the test when they both have say...2000 hrs. on them.