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WOT RPM too low

T

tim_pinder

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"I just bought a brand new 200

"I just bought a brand new 2008 Alumacraft Navigator 165 with a 2008 Evinrude E-TEC 90hp.
The motor is mounted so that the anti-ventilation plate is 1/2" above the bottom of the hull at its deepest (bottom of the "V").
I have a 13.25" X 17" Michigan Wheel Apollo 3-blade stainless steel propellor (it came with a 13.25" X 17" aluminum).
After breaking it in for about 1.5 hours changing speeds every 5 minutes or so between 2900 and 4500 RPM, I went to WOT but only got 4800 RPM and 36.5 MPH, trimmed right up. It had less than 40 liters of fuel (10 gallons) and myself (205 lbs) and my friend (210 lbs).
Boat/engine tests I've found on-line indicate the E-TEC 90hp on this boat should go over 40 MPH at close to 5500 RPM.

I've been reading this site and it looks like there's a lot of people in "the know" here.

Could anyone help me with why my motor is not performing as it should or what I can do to fix the problem??

Thank you so much!

Tim"
 
"I retired some years before t

"I retired some years before that engine was manufactured. If carburetors exist (engine not running), remove the carburetor face plate, put engine into forward gear (spin prop while shifting to align shifter dog).

Now, apply full throttle while observing the throttle butterflies.

If the throttle butterflies do not open fully, therein lies your problem. Let us know what you find."
 
"This engine does not have a &

"This engine does not have a 'movable' timer base, it is all in the EMM.
The question should perhaps be how it performs with the delivered prop?"
 
"Morten..... No timer base, ne

"Morten..... No timer base, never too old to learn something new. The thought keeps coming back to me, a saying I heard about 50 years ago.... "Sophistication breeds problems"."
 
"Joe.
What in general is used

"Joe.
What in general is used is a CPS - Crankshaft Position Sensor. It functions similar to the old diesel rev counter that counted the teth on transmisson gears, but this one 'counts' some special casted notches on the fly wheel. The signals are transmitted to the ECM which then depending on engine rev, load (butterfly opening), barometric pressure, engine temp, air intake temp fires ignition at programmed time!
Very simple, hardly any moving parts that might get stuck, only half a dozen sensors that might fail!!!
The old Fichts had a rather funny cable routing, and sometimes the CPS got interference signals from other cables messing it all up completely! Now wonder they blew up!
Messing with cable harness and routing on these engines, not to forget spark plugs may really create a havoc. This is not only E-tech, goes mainly for all the EMM controlled injected engines."
 
"I took the boat back to the d

"I took the boat back to the dealer and they raised the motor up another hole, so now the anti-ventilation plate sits about 1.5" above the bottom of the hull. I'm no longer dragging the plate through the water and that gave me another 200 rpm and 2 mph, but I'm still 500 rpm short of the top of the manufacturer's suggested operating range and not getting all that I should from the motor.

I'll try what Morten suggested and switch out the 13 7/8" X 17" stainless steel prop I bought with the 13 1/4" X 17" aluminum that it came with and see if that helps. I've read elsewhere on this site that unlike stainless props, aluminum props flex a little, thus an aluminum prop with a theoretical pitch of 17" actually has a pitch closer to 16" under load. Perhaps I'm a little over propped then with that stainless steel? I'll find out soon enough.

Thanks so much for the help! This is my first boat so this is all new to me and the dealer isn't sure what the problem is.

Thanks again,

Tim Pinder"
 
"If not mistaken the 90 E-tech

"If not mistaken the 90 E-tech has a max range of 4500 - 5000. If I got it right You are now at 5000, which i where You will obtain the max rated HP of the engine.Speed is 38,5 mph, and I guess it is with the same load as last time. I think it looks rather spot on. 'Loose' Your friend, and You might get another 1,5 mph! What the test probably did not show, was air temp, barometric pressure and the specific prop used? My guess You are as close as possible."
 
"It's actually a very wide

"It's actually a very wide range, 4500 - 5500 rpm. Maximum horsepower is at 5,000 rpm though, you're right, I just confirmed that. Here's an engine/boat test:

http://www.evinrude.com/EvinrudePublic/CMSResource.ashx/www.evinrude.com/en-US/E ngines/2007/ETEC90/PDF/PE502.pdf

I've actually looked at several engine tests, and even the 75hp E-Tec pushing that boat went faster with higher rpm than my 90hp (same block), which is what alarmed me. It's for fishing, not racing, so as long as I'm at a range that's not causing longterm wear, I'm satisfied. I was just hoping to get the most out of it.

I've also heard that Evinrude programs the E-Tec to use twice the oil and limit rpm for the first 10 hours over 3000 RPM or so, but I haven't been able to find verification of that on their website.

I'll still try swapping props, but if 5,000 rpm is where it should be and won't wear the engine (I've heard WOT below manunfacturers recommendation can cause longterm damage), then I'm happy.

Thanks,

Tim Pinder"
 
"Looking at the performance da

"Looking at the performance data, I would say You are within reason. The prop You are using seems to give some more bowlift (raked) than the one on the test. However the tested one might have some more blade area, and the engine is not that high (1st hole up).
Yes, the engine gives 'double oil' for the first 10 hours ABOVE 3000 rpm,however it should not be a rpm/power limit as far as I know.
If the test was performed at sea conditions like the pick, they were running under optimum conditions giving max of air under the hull compared to 'flat' sea."
 
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