dissappointed in new Viper stainless steel prop.

[the brain]

Shakedowns w/ new viper prop. on 2012 Evinrude ETEC gen1 175hp About the same as the aluminium of exact same pitch.but tad wider in diameter I think the Aluminum has more cupping.

At 5K RPM 42MPH thats trimmed in RPMs will not increase from 5K unless I trim up then I only increase speed by less than 2MPH.

I have been informed the midsized ETEC stops making power higher the 5K RPM.


I am dissappointed in the Viper not making at minuim 5MPH more than Aluminum.was hopping for 49MPH or even 50MPH

props:
Viper 14 3/4x19 RTR #0763918

Johnson Evinrude Outboard Aluminum Propeller 391201 14.5x19



I haven't configured the high threshold for the load meter notice how it shoots quickly very close to 100% after 3.500RPM.

Not sure what the load meter is mearsuring maybe how hard the engine is working?I just now learned what load is it's basicely the amount of throttle.


Conclusion: not much of an increase in MPH after 5K RPMs w/ either prop. maybe squeezing 1 1.5MPH top speed increase w/ Viper over the Aluminum. Was hoping for more.


I have also been informed that these midsized ETECs prefer a 14.25 diameter. Maybe 14.75 (half inch) makes the differnce BC the aluminum is .25 less diameter at 14.5.


don't wanta be constantly swapping props. For a tiny increase.


think I'll be staying at 5K RPM an be satisifed w/ 42ish MPH.




here's the aluminum on the Ray both the HDS8 an Ray use the Garmin GPS antenna for SOG.
additionaly I was hopping the HDS8 would display the correct depth.
ony the Ray has a transducer thought the HDS8 would recieve this dept. data over NMEA2K? the #s the HDS8 is displaying isn't even close to the Rays.
please advice where my expectations realistic w/ the stainless steel Viper.?

 

[fallguy]

The engine’s rated hp is at 5350. And the AI agent says 5850 is max. Why would you not want to run 5500?

 

[the brain]

The engine’s rated hp is at 5350. And the AI agent says 5850 is max. Why would you not want to run 5500?

this 5K RPM is trimmed all the way down won't increase untill I trim up.

 

[HelmutSheina]

Mr Brain I found a HP curve for an unknown year 150Hp eTec, which should be very similar to your engine. It does level out as you said, but still beats Yamaha & Honda 4 stroke 150s and I'd assume the torque curve continues to rise until the 6K RPM max rating.

Maximum RPM is measured at optimal trim and the minimum for your model, with no room for a heavier load, is 5400 and you need to be shooting for as close to the 6K max as possible.

Some motors will catastrophically fail if overloaded. I don't know if the eTecs are prone to it, but earlier Johnson/Evinrude models sure were, overloading two stroke outboards is a dangerous game.

 

[baeckmo]

This has been discussed before, see your previous thread on propeller selection, and I have repeatedly shown in this forum that the E-tec engines deliver maximum hp at rpm's below 5000. Sadly, this info does not find its way into the brains of those who believe that screaming rpm's equals high boat speed..... The diagram Helmut S presents above shows a max power of 165 hp @4500 rpm, sinking to 160 @ 6000. In some E-tec variants the difference is even larger. To the OP: why do you think that a power of 160 hp should push your boat to a higher speed than 165 hp?

In your case, with an E-tec of nominal 175 hp, you will find that it actually produces more than that in the range just above 4500 rpm, provided you use a prop that lets the engine operate there!

 

[fallguy]

I don’t think my query was unfair or deserved any snark. And it was only a question. I appreciate learning E-Tecs generate more hp at a lower rpm; it is actually rather interesting; I have not looked closely at prior remarks.

Just cup the stainless more or take it to 19.5 pitch at a prop shop and see what happens.

49 • 19.5/19 = 50.2

Don’t expect 5 mph.

 

[the brain]

Mr Brain I found a HP curve for an unknown year 150Hp eTec, which should be very similar to your engine. It does level out as you said, but still beats Yamaha & Honda 4 stroke 150s and I'd assume the torque curve continues to rise until the 6K RPM max rating.

Maximum RPM is measured at optimal trim and the minimum for your model, with no room for a heavier load, is 5400 and you need to be shooting for as close to the 6K max as possible.

Some motors will catastrophically fail if overloaded. I don't know if the eTecs are prone to it, but earlier Johnson/Evinrude models sure were, overloading two stroke outboards is a dangerous game.

View attachment 210779

I would like to see this HP power curve an torque curve on same graph. we all know torque is the power that makes propulsion. to me HP#s are fluff marketing #s. apparently these ETECs have a flat torque curve thats why they take off out the hole so stronge.
what I really want to know did I select the correct size prop. for my engine an hull. just dissapointed in only a less than 2MPH increase over aluminun of almost same size diameter an same size in pitch. thanks

HelmutSheina​

 

[the brain]

This has been discussed before, see your previous thread on propeller selection, and I have repeatedly shown in this forum that the E-tec engines deliver maximum hp at rpm's below 5000. Sadly, this info does not find its way into the brains of those who believe that screaming rpm's equals high boat speed..... The diagram Helmut S presents above shows a max power of 165 hp @4500 rpm, sinking to 160 @ 6000. In some E-tec variants the difference is even larger. To the OP: why do you think that a power of 160 hp should push your boat to a higher speed than 165 hp?

In your case, with an E-tec of nominal 175 hp, you will find that it actually produces more than that in the range just above 4500 rpm, provided you use a prop that lets the engine operate there!

yes you have mentioned the no increase in power above 5K RPMs but that comment could use some clairification. notice how the tack stays at 5K thats bc engine is trimmed down all the way. this RPM increases only when I trim upward.

are you saying this is normal an I should get used to trimming up well before I hit the 5K wall?

I thought the procedure for testing a prop was trimmed down all the way?

most importantly did I select the best prop. for my engine an hull even though I basicely only increased speed by 1.5MPH?

"OP: why do you think that a power of 160 hp should push your boat to a higher speed than 165 hp?" I assume bc it's more power ?
thanks baeckmo

 

[the brain]

one more issue I neglected to mention was all prior shakedown runs where conducted using a 6 gallon portable fuel tank which has a 1/4"inside diameter fuel pick up tube.
this latest shakedown w/ new Viper prop. I used the proper sized fuel tank w/ a 3/8"Inside diameter fuel tube you would assume that the 1/4" pickup was choking off the fuel supply but evidently has little to no effect on performance decrease.

so in reality I was actuely expecting even more than 5MPH increase from just prop upgrade to stainless steel an engineered by BRP. was also expected better proformance w/ the larger fuel supply tube feeding what the ETEC needed.

which makes this even doubleing the dissapointment.

here's the little portable.

 

[the brain]

I don’t think my query was unfair or deserved any snark. And it was only a question. I appreciate learning E-Tecs generate more hp at a lower rpm; it is actually rather interesting; I have not looked closely at prior remarks.

Just cup the stainless more or take it to 19.5 pitch at a prop shop and see what happens.

49 • 19.5/19 = 50.2

Don’t expect 5 mph.

no snark intended hope you know I appreciate your advice.

 

[baeckmo]

we all know torque is the power that makes propulsion. to me HP#s are fluff marketing #s.

That is where you get it all wrong. The hull needs (thrust x speed), ie POWER for a specific operating point. This power comes from the engine, that is delivering (torque x rotational speed), ie POWER to the propeller. So, unless the power delivered by the engine matches the power required by the hull, you won't get the hull speed you want!

You have to match the propeller so that your engine operates on the rpm's where its power is peaking. The E-tec 150 shown in the diagram has its maximum torque ~276 Nm @ 4000 rpm; at 6000 it delivers 187 Nm. The torque that produces 165 hp @ 4500 rpm is ~257 Nm.

The fat power curve of the E-tec in the diagram means that it has more power than the other engines all the way from just below 2000 rpm and up to 6000. When you compare that with the hull power requirement from low speed and up, this means that it has more "surplus power" to accelerate the boat than the other engines shown. But at 6000 rpm, they all produce 160 hp to the propshaft. Everything else (like lower gearhousing drag and boat drag) identical, they all will give you the same top speed. When talking top speed, forget all the nonsense you hear about torque, the only thing that matters is POWER! And correct prop selection!

 

[Skip Johnson]

I would like to see this HP power curve an torque curve on same graph. we all know torque is the power that makes propulsion. to me HP#s are fluff marketing #s. apparently these ETECs have a flat torque curve thats why they take off out the hole so stronge.
what I really want to know did I select the correct size prop. for my engine an hull. just dissapointed in only a less than 2MPH increase over aluminun of almost same size diameter an same size in pitch. thanks

HelmutSheina​

Two props stamped as 19" pitch may not actually be the same pitch particularly if only one is cupped.

Quite some years ago a switch from a 3 blade aluminum to a 3 blade ss prop on a 16' Larson with a 115 hp Johnson 2 stroke (last of the 90 degree V4's) made measurable improvement in hole shot and top end for that specific case.

I'd get the new prop cupped by someone who knew what they were doing,

 

[baeckmo]

....So, to continue from my post #11, if understanding the interaction between torque, shaft rotational speed and power is chapter one here, then the chapter two is about the propeller and its interaction with the engine and the water.

To create the force that pushes the boat through the water against the drag from hull and outboard leg, the propeller must convert the mechanical POWER (torque x rotational speed, remember?) in the rotating shaft into hydraulic POWER (equals flow x pressure). This conversion comes with hydraulic ("pumping") losses, which consume some of the shaft power.

This means that a certain prop may have its maximum efficiency (=minimum losses) say 63 percent and letting the engine hit 5000 rpm, where you have the power 165 hp. The resulting hydraulic power driving the boat is then 0,63x165=104 hp.

Now you have another prop that has a slightly higher efficiency, say 65 percent, but lets the engine spin to 6000 rpm, where it produces 160 hp. The hydraulic power is now 104 hp again, which means no increase in pushing force.

You might even stumble upon a screw that has 65 percent efficiency, but the engine only reaching 4250 rpm. Looking at the power curve above, you find that the E-tec is still producing 160 hp at this point, and the hydraulic power will again be 104 hp. The critical difference here is that you would get the same top speed, but the "surplus power" for acceleration or increased load is lower.

The real trick is to find just that unique screw that has its maximum efficiency at the rpms where the engine power is peaking. Adn the closer you get to the possible max, the smaller are the differences. It will finally boil down to the environmental testing conditions; is it calm flat with no wind, is there the tiny ripples from a morning breeze or a bit ruffle from yesterdays gale?

I'll be back with comments on the trimming issue later; got to celebrate the missus' birthday now!

 

[HelmutSheina]

Mr Baeckmo I understand what you are saying about propping these eTecs to 5K RPM, but are we not obliged to follow manufacturers specs, which say prop to 5400-6000 RPM range for whatever reason?

I cannot justify this max RPM requirement in light of the power curve, but training and experience dictate that if they spec say 50mm fuel lines, then the boat will be delivered with that, or with what the designer specs if the boat is a one off. Otherwise the installer likely assumes liability in case of failure, and failures in the marine environment are common.

Standard procedure dictates that boat engines are propped towards the higher end or their range to cover high loadings. A piston or valve can fail in seconds if combustion temps escalate, though EMS should have addressed this.

I found similar with the mid 80s OMC 90° loop charged V4 & V6, huge heavy fuel sculling blobs. They seemed to peak at around 4500 RPM, and were better performing all round with meatier props. The V8 was likely the same,, but I avoided them or they avoided me.

 

[HelmutSheina]

Mr Brain max RPM is usually measured under running trim, not with the motor right down.

I agree with what Baeckmo is saying re RPM, but 45 years of years of blind obedience to factory specs trumps logic on this one. Though the manufacturer no longer loves their eTecs so I think Brain Manufacturing gets the call here.

Poke around in eTec forums and get a feel for how the V6 versions handle overloading (any situation with max RPM below 5400)? Older two strokes may have melted a piston and put a rod out the side in seconds, but EMS and flat top pistons on these might possibly prevent it.