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Author Topic:   2008 E-TEC 135-HP Twin with Unequal WOT RPM
Don SSDD posted 08-18-2015 03:57 AM ET (US)   Profile for Don SSDD  
My friend has [counter rotating 2008 model-year Evinrude E-TEC 135-HP engines] on a [1994 Boston Whaler] GUARDIAN 25. One engine peaks out at 5,700-RPM and the other at 5,200-RPM. He had [the E-TEC engines] checked out by a shop. He was told there was a problem with a flutter valve in the exhaust that would require replacing and would mean a lot of labor to fix it and parts. He was told this is a common problem with E-TEC engines, and quite often happens with one of the outboards on twins. That doesn't sound logical that twins or non twins would cause a problem. Ever heard of anything like this?


seahorse posted 08-18-2015 07:58 AM ET (US)     Profile for seahorse    
Don--the E-TEC 135-HP does not have a "flutter valve." I assume the person meant exhaust valve for tuning which is used on other models of E-TECs but not on the V6 135-HP engine.

The 115-HP and the 130 HP V4 engines do have a movable valve in the exhaust section. Exactly what motor does your friend have?

Don SSDD posted 08-18-2015 08:39 AM ET (US)     Profile for Don SSDD    
Seahorse, my apologies, I am guessing they are 130HP V4's, I will get the exact numbers off them so I know what they are. I started this thread without using my brain, which loses too many things to rely on it for good information.


jimh posted 08-18-2015 08:41 AM ET (US)     Profile for jimh  Send Email to jimh     
I have never heard the term "flutter valve" before. I can't find any instance of that term being used with an E-TEC outboard. Compare at

I think you'd be more likely to run into a problem with a flutter valve in a hospital emergency room than on a boat with twin E-TEC engines. Maybe that outboard engine technician is really an E.R. doctor moonlighting.

Don SSDD posted 08-18-2015 04:29 PM ET (US)     Profile for Don SSDD    
The motors were built 11/2008, E130DPXSES for both, one had the lower unit changed to counter rotating. The outboards decodes as 25-inch 130-HP, power steering, electric start. The Whaler had twin 1996 Johnson 150's on it before, they re-used the same propellers on the E-TEC engines.

I don't know what training the technician has, they are not an E-TEC dealer, but are supposed to be good.

I think what Seahorse is describing (movable valve in exhaust system) is possibly what the technician is calling the "flutter valve". Does a problem there cause a reduced maximum RPM?

I know web site diagnosis based on what little I have been told is an problem--third or fourth hand information.

My reason for asking this question here is to find out if anyone has heard of this "problem that is common in twin E-TEC engines". If there is a problem common to E-TEC engines (caused by a movable valve in the exhaust), why would it only happen in a twin setup?

When I am able, I will speak with the technician and with a local E-TEC dealer to find out exactly what is being diagnosed as the problem and the solution. I think the technician also said this problem did not set a code in the computer system.

Thanks for any help or information.


acseatsri posted 08-18-2015 06:22 PM ET (US)     Profile for acseatsri  Send Email to acseatsri     
I don't think it has anything to do with the twins but rather by having a seconnd baseline engine that you normally wouldn't have, you're able to see a distinct difference between the two engines. Without the baseline, I think a single engine would probably exhibit the loss of RPM gradually so as the loss wouldn't be evident, perhaps being dismissed as just a result of a heavier load or a slightly fouled bottom.
Hoosier posted 08-18-2015 06:48 PM ET (US)     Profile for Hoosier  Send Email to Hoosier     
Tell him to have his throttle cables calibrated, if he has an 'analog' system, not [ICON ETS electronic throttle and shift]. It sounds like one engine has its WOT stop set wrong. I have this problem with my twin Yamaha F-150s, one cable has more slop than the other so they're a bitch to synch.
Don SSDD posted 08-18-2015 07:48 PM ET (US)     Profile for Don SSDD    
Not [ICON ETS electronic throttle and shift], would be great if that is what it is. Reused the same Johnson controls.


jimh posted 08-19-2015 07:46 AM ET (US)     Profile for jimh  Send Email to jimh     
The E-TEC uses a method of tuning the exhaust path to enhance the performance of the engine. A valve--I think it is more likely described as a similar to a throttle plate--operates from an electric actuator. The valve changes the effective length of the exhaust path.

As for the use of this technique on twin engines, and the twin engine configuration causing problems, I don't see a basis for that.

It seems more likely that a problem with a valve in the exhaust path of an engine could be caused by the exhaust having too much soot, which might then collect on the valve and interfere with its operation. Too much soot in the exhaust is a result of the engine having too much load on it, or lugging.

If the V4 130-HP engines are trying to turn the same propellers that were used with V6 150-HP engines, the propeller pitch may be too high. This would cause the 130-HP engines to be lugging, and producing more soot in the exhaust. That might be causing a problem with the exhaust valve operation.

If the exhaust valve does not operate properly, that engine will produce less power output. That would manifest as lower engine speed.

jimh posted 08-19-2015 07:53 AM ET (US)     Profile for jimh  Send Email to jimh     
Other possible causes for unequal engine speed at WOT with twin engines and counter-rotation could be:

--influence of the counter-rotating gear case; there may be more mechanical friction in the counter-rotating gear case;

--influence of left-hand propeller; the left-hand version of the propeller, even though marked with the same pitch as the right-hand one, may not be perfectly matched in terms of the load it produces on the engine;

--influence of the hull and engine mounting; perhaps there is some aspect of how the engines are mounted or how the hull form runs that favors one engine over the other due to factors like toe-in or toe-out, water flow disturbances, and lateral trim on the boat.

Don SSDD posted 08-19-2015 07:56 AM ET (US)     Profile for Don SSDD    
That sounds logical Jim. With the present setup, if you are running constantly at an RPM that lugs the motors, would a good long run at say 4500 or higher burn off the soot?

It wouldn't solve the problem but if this did burn off the soot, and the engines could run up closer to the say 5700 RPM, a new set of props might solve the problem?

I'll see if I can find out what props are on there now.


Qtrmeg posted 08-21-2015 02:24 PM ET (US)     Profile for Qtrmeg  Send Email to Qtrmeg     
Could be a bad tachometer. Try running each engine alone and see if the [boat] speed is the same.

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