Etec prop sizes.

[steelespike]

As everyone knows I'm an Etec fan.
I was doing a little research and was surprised at the Etec prop sizes.
I know gear ratio enters into this but the Etec surprised me specifically on pontoons but also more normal applications.
In a brief look I only found 2 Etecs And a 50 Merc. bigfoot.
Big foot is 2.33 gear ratio. I picked the Merc because the gear ratio was closer to the Etec.On a 20 ft Duracraft pontoon 1620 lbs. prop is a 14 X 9 aluminum. made 18.9 mph at an impressive 4.2 gph.5325 rpm.
The 50 Etec 2.63 stock ratio on a 20ft Premier 1,800 lbs.prop is an aluminum (this is impressive) 14 X 13 made 21.1 mph at a slightly less impressive 4.96 gph.5,500 rpm
Same motor on a 23 ft Maurell pontoon 2,455 lbs Stainless (also impressive) 13 3/4 X 13. Made 19.5 mph at a not to impressive 5.16 gph.
5,375 rpm.
Not sure what all this says about slip,torque curves etc.But in just the prop size I think the 14X13 on a 50 hp pontoon is impressive.
I also think I have too much time on my hands.

 

[Silvertip]

Re: Etec prop sizes.

When you compare fuel flow (GPH), speed, and RPM you need to compare speed -- not GPH. You will find that at a given speed two engines will run at drastically different rpm even though the speed is the same. An engine running fast will burn more fuel than one running slow. As you found out, the E-tec was faster, pushed a heavier boat with only slightly less fuel economy at wide open throttle. Had you run the E-tec at the same speed as the Merc the E-tec would have had the same or better fuel economy -- still on a heavier boat.

 

[steelespike]

Re: Etec prop sizes.

When you compare fuel flow (GPH), speed, and RPM you need to compare speed -- not GPH. You will find that at a given speed two engines will run at drastically different rpm even though the speed is the same. An engine running fast will burn more fuel than one running slow. As you found out, the E-tec was faster, pushed a heavier boat with only slightly less fuel economy at wide open throttle. Had you run the E-tec at the same speed as the Merc the E-tec would have had the same or better fuel economy -- still on a heavier boat.

I was just listing the the data; wording made it look like a gph comparison.
However when the Etec is run at 19.2 the closest next data it gets 3.73 gph.As rpm comes down Merc has a slight edge in GPH. but loses out on
speed and thus MPG.At about 2,500 Merc starts to lose the gph,mph and thus mpg until at 1,000 Etec is at 18.4 mpg and Merc is at 12 mpg.Of course at about 3 mph who cares.

 

[Silvertip]

Re: Etec prop sizes.

If you search the forum, about a week ago I posted a comparison of a 75 E-tec, & 70 Yamaha 2S and 75 Yamaha 4S on an Alumacraft Navigator 165 CS and showed Speed, MPG, and GPH at various RPM. If you find that post, that more clearly shows the relationship between those factors. The reason I mentioned that is I will follow up that post by adding figures from my own Navigator 165CS which is powered by a 75 Merc 2S. I run a fuel flow monitor and early next week I will add my figures. I can guarantee you that all four of these motors burn nearly identical amounts of fuel at wide open throttle. But that's just physics. It's the low and midrange speeds where the technology shows up. Stay tuned.