posted 09-07-2008 08:28 PM ET (US)        

http://continuouswave.com/whaler/reference/ETEC250HO.html

I will be glad to try to answer them here.

posted 09-07-2008 09:30 PM ET (US)            

The new engine looks great on your boat. I look forward to reading more about your experiences with the new power, especially the improvement in fuel economy.

posted 09-08-2008 01:35 AM ET (US)            

very informative article. If anybody asks for a new (modern) motor, that is the factual reply.

posted 09-08-2008 03:07 AM ET (US)            

In the 2nd paragraph, you say it's a 2007 model but in the acknowledgement, you state that it's a 2008. I see it was manufactured in 12/07. Does that make it a 2008 model year?

posted 09-08-2008 05:35 AM ET (US)            

Erik

posted 09-08-2008 08:11 AM ET (US)            

Perry -- Jim's Evinrude 225, when built, was about 225 HP, of course its 16 years old too so its hard to say whether he's still getting 225 HP from it. The 250 HO is a 250+ HP motor and given the HO badging, it is probably closer to 275 HP than 250 HP. So there is probably at least a 75 HP difference between the motors and thus the ratio is more like 1.10 than 1.05. A 1.10 ratio should produce 43 MPH assuming that the 225 is 225 and everything else being equal. But then not everything else is equal -- different propeller design with larger diameter (moves more water, perhaps better bite in the aerated water too) and a slippery Lightning-2 (L2) gearcase versus the old Offshore (O-type) gearcase.

posted 09-08-2008 09:00 AM ET (US)            

Hard to turn down the prospect of 53 percent more boating for the same fuel cost.

posted 09-08-2008 09:09 AM ET (US)            

When the boat is lighter, the weather is cooler, and the 225-HP can swing a 17-inch propeller to maximum speed, it can reach 41-MPH. Actually, one very crisp fall day with the boat stripped down to almost a bare hull the 225-HP hit 42.5-MPH, its all-time record. But in the warm summer weather and with a full load of gear, it winds up to about 38 to 39-MPH at the top. That is the same conditions in which the 250 H.O. was tested, and that is the proper comparison. Every pound you add to the boat reduces speed. Having the canvas up and rigged reduces speed. All these things affect the speed. You can't say, "Oh, that boat ought to go 45-MPH." It depends on the load and conditions.

I would not characterize the boat has previously having a poor set up. I have run a dozen different propellers of many brands and styles, and the results are quite close. People who are not familiar with a Whaler Drive may have expectations of speed from them that are not realistic. A Whaler Drive is not a speed-enhancing device.

In the article I say:

"It would be inappropriate to attribute all of the improvement in speed obtained with the new motor to the greater power of the engine itself."

I can't say it any more explicitly than that. There are other influences. Some data I have shows the 250 H.O. is making about 270 to 275-HP at peak. How much power does my 16-year-old 225-HP motor make? Who really knows?

posted 09-08-2008 10:27 AM ET (US)            

You now have reignited my itch to upgrade from my older 1988 200 HP (carbed ) Yamaha. I always talk myself out of the expense right now saying the current engine runs like a champ (touch wood) and the fuel savings would never make up the cost and expense to upgrade. And with two kids in college right now it is definitely a luxury expense.

I am guessing your engine was running fine since we never heard otherwise. What were your deciding factors in biting the bullet and repowering the Revenge. I am also guessing that you plan to install a NMEA network and a new Lowrance unit with the e-Tec Lowrance adapter.

posted 09-08-2008 11:46 AM ET (US)            

As far as aesthetics go, the blue paint and flag graphics really look good on the Revenge, with your actual flag visually tying the outboard to the boat. The size of the E-TEC is very much in proportion to the boat, and it looks correct sitting on the Whaler Drive.

posted 09-08-2008 11:47 AM ET (US)            

What I would really like to see is the comparison of this E-TEC and your old motor using the same propellers (or same models of propellers pitched accordingly). I suspect some of the gains in fuel economy may be due to the prop.

The application of the HO model to this boat is a little unusual. Apart from any difference in peak horsepower, the gear-cases are different between the HO model and the standard E-TEC models.

I believe the HO uses a 1.75:1 gear ratio where the standard E-TEC uses a 1.86:1 gear ratio in the more robust offshore gearcase design. The latter would be better suited the cruising you do in your Revenge.

posted 09-08-2008 02:54 PM ET (US)            

Enjoy the motor, it would be tough to go back to your old motor. Perhaps the boatshop that offered to do this for you, considering your relationship and website, knew that in advance. He did a nice rigging job and probably has a upcoming sale!

Have fun

posted 09-08-2008 05:28 PM ET (US)         

I hope you decide to stay with it, so that you will now be able to comfortably keep up with the rest of the crowd in cruising speeds, and have extended range too. I think the SportMaster type gearcase looks great also.

And for a card carrying Republican like you, the flag graphics go nicely with the boat. I didn't think I would like that look, but actually do. Go for it! Going back will not be easy.

posted 09-11-2008 05:58 PM ET (US)            

The 225-HP V6 pushes the boat to 39-MPH and gets about 1.75-MPG at that speed. From this we can derive the gallons per hour:

(1-GAL/1.7-MILES) X (39-MILES/1-HOUR) = 22.3 GAL/HOUR

We estimate that the brake specific fuel consumption (BSFC) of the motor is around 0.6-LB/HP-HOUR. If the fuel weighs 6.125-LB/GAL, then this implies

22.3-GAL/HOUR x 6.125-LBS/GAL x 1-HP-HR/0.6-LBS = 227-HP

Now we really don't know if the 225-HP motor is making about 227-HP, but it is certainly burning enough fuel to do so.

Previously I predicted that the improvement in fuel economy for a direct-injected two stroke with a BSFC of 0.44 would be on the order of 25-percent. This estimate was made long before I had any actual data from the test of the E-TEC 250 H.O. In the test period covered in my article, I noted that the improvement at higher speeds was on the order of 32-percent. This is fairly good agreement with the prediction, which, after all was just based on an estimate of the BSFC of the direct-injection engine. Also, as I pointed out, there may be other factors which contributed to the improved performance, such as the propeller and the gear case. Allowing for those influences to account for the extra 8-percent improvement seems quite reasonable.

posted 09-11-2008 06:31 PM ET (US)            

quote:

---

At about 1,000-RPM the E-TEC pushes the boat along at a nice no-wake speed of 5-MPH and gets 25-MPG, an amazing improvement--sixteen times better fuel economy. I better repeat that for emphasis: the boat gets 25-MPG at no-wake speed.

---

posted 09-11-2008 06:55 PM ET (US)            

I re-read your thread: Brake Specific Fuel Consumption and noticed that you said, "actual fuel savings might be significantly higher, more like the 50-percent reported by enthusiastic owners of new outboard motors."

posted 09-11-2008 07:20 PM ET (US)         

What is interesting is how costly the Whaler Drive is in overall performance, both in speed and fuel economy, because of drag and additional weight. The differences are amazing, assuming the Optimax 225 puts out the same HP as the old carbureted Evinrude 225. The Whaler Drive even completely negates the additional 270 HP of the 250HO, while at the same time cutting fuel economy in half.

posted 09-11-2008 08:21 PM ET (US)            

In my test data the boat is not a factor, because the boat is the same boat. The data acquisition is not a factor because the data is acquired by the same devices. Further, the test conditions are very similar, similar water, similar waves, similar general conditions, with, if anything, a disadvantage for the E-TEC due to higher temperatures.

To use my data and then make a comparison to a different boat, with a different motor, with data acquired by different instruments, in quite different test conditions such as very much colder water and weather, requires far too many assumptions to hope to have any possibility of being valid.

It would be interesting some day to discover the influence of a Whaler Drive on the performance of a Boston Whaler hull, but you cannot possibly do that here.

posted 09-11-2008 08:49 PM ET (US)            

Some of your additional speed probably comes from getting the bow up. Maximum Lift to Drag for a planing V hull typically occurs at trim angles above the trim angle that causes porpoising. Since you were trim limited with the old motor and never mentioned porpoising you never had as much trim as you could have used for top speed. With the new motor and a better cg location you are getting a better trim although even more might be better.

posted 09-12-2008 09:39 AM ET (US)            

I think you might want to go back and refresh your recollection. After that, you might consider cross checking Mercury's test reports for the Optimax 225 where you will find that even a 57 MPH aluminum Tracker tested by your favorite publication, Bass & Walleye Boats, doesn't get better than 4.1 MPG. I'm willing to bet that JimP's 30 MPH fuel economy is significantly less than 4 MPG and more likely in the 3.5 MPG range.

Regarding the Whaler Drive -- saying that the WD cuts the fuel economy in half is just wrong. As I've said many times, it should be viewed as a hull extension, turning a 22 Whaler WD into a 24 foot boat. A 22 Revenge WD is more like a notched transom 25 Revenge than a notched transom 22 Revenge. Thus, the performance of a 22 Revenge WD, such as JimH's, should be compared to other 24 foot boats, such as an Aquasport 246 (24'6") of similar vintage, or to a classic notched transom 25 Revenge.

posted 09-12-2008 11:42 AM ET (US)            

1-GAL/25-MILES x 5-MILES/1-HOUR = 0.2 GPH

Just yesterday it happened that I spoke with the manufacturer of the fuel flow sensor I used and he alerted me to the potential for a decrease in accuracy in the flow measurement when the rate is below 1.3-GPH. This puts some doubt about the accuracy of my low-speed MPG measurements, but I will explain a bit further about how I derived that number.

When running at low speeds the fuel economy indicated was generally fluttering over quite a range of numbers, and most of the time was shown to be higher than 25-MPH. After watching the readings for several minutes, and noting the range, 25-MPH was about the lowest reading ever displayed, and so that is the number I reported. The flow meter is set to have a lot of dampening, and the values it reports are integrated over a period of time (about 20-seconds). When making a measurement you have to let the flow rate stabilize for at least 20 seconds. For these low speed readings we let the rate stabilize for several minutes. Then, in the case of the 5-MPH figures, because they were reading so very high, we discarded all but the lowest values. which were roughly 25-MPG.

I don't think this number is precisely accurate, but it is not unreasonable. Wake making generally increases with speed, and making wake at displacement speeds uses up a lot of energy. My boat has a nice long water line, and it can be driven at 5-MPH with very little wake being produced.

Average fuel economy is derived from the sum of all speeds of operation, but there is an odd and not always obvious relationship between those data points. The better the fuel economy at a particular speed the less fuel is burned at that speed. Because the average fuel economy is influenced by the amount of fuel that is consumed at that rate (and not by the time spent at that rate), the influence of any one data point on the average fuel economy decreases with increasing MPG at that data point.

You can see this in the data in my report. Over half the time we were at low speed operation where the fuel economy was typically 5 to 25-MPG. Yet the overall average fuel economy was only 2.63-MPG. This is because the average is much more heavily influenced by the fuel economy figures from high speed operation, where most of the fuel is burned. The high-speed operation fuel economy is more in the range of 2 to 2.65-MPG. So even though almost 55-percent of the time was spent in low speed operation, all that great fuel economy only dragged the average fuel economy upward slightly from the high-speed average. Again, that is because fuel economy figures have to be weighted by the amount of fuel burned at that rate, not by time.

The most remarkable thing about the low speed operation of the E-TEC 250 H.O. is just that it gets better fuel economy at low speed than high speed, which is the opposite of the old 225-HP V6. It got its worst fuel economy at low speeds!

I was thinking that I could get a better measurement of slow speed fuel flow by using an auxiliary tank to feed the engine. Then I could run at 5-MPH for an hour and see how much fuel was actually used. The problem with that idea, however, is that with a 250 H.O. on the transom it is hard to run at 5-MPH for an hour.

:-)

posted 09-12-2008 11:47 AM ET (US)         

The overall performance of Whaler Drive boats should be similar to that of a boat 2' longer of similar hull design. And even at that, the performance differences in terms of speed would be very difficult to calculate and would largely differ only in that the 24' boat would likely weigh slightly more, and thereby slowing down the 24' boat a fraction of a MPH.

For those who accept the equations for speed prediction of Crouch and that of the "propeller calculator" (I was very skeptical of Crouch at first, and still believe there is some limitations, but overall it very helpful) on this site, consider this. There is no provision for boat length in either of these equations. If boat length was a significant characteristic in predicting speed or performance, I would think there would be some provision to account for this. Instead, Crouch assumes that if you have similar hull styles and overall weights, whether one is 22' or 24' is insignificant in predicting the speed of the hull, assuming all other factors are similar as well.

posted 09-12-2008 01:55 PM ET (US)            

Sweet!

Very similar results to what happened to me in 2003 when I replaced my 1989 225 carbed Johnson with a 2003 225 Merc Optimax - speed (top & cruising) and mpg both increased significantly.

Several comments:

1. On nice days - TAKE THAT CANVAS DOWN! It slows you down and increases noise at the helm.

2. Whaler Drive: In the 5th picture it looks like the WD has a slight "hook" that might drive the bow down. I don't notice the "hook" in the 3rd picture. Is there a hook or is it just the angle of the picture?

3. Add trim tabs. In the 10th picture it looks like you have a slight list. With the trim tabs on my 1990 Revenge 22 W.T. I use the tabs all the time as passengers change seats and as the dogs wander from side to side. Also, the tabs help you plane at a much lower speed.

posted 09-12-2008 02:09 PM ET (US)            

1983 V22 Revenge notched transom
1992 200 Evinrude E200TXENE

WOT 41 mph
cruise 3700 rpm, 27 mph, 2.6 mpg

These are an average. Sometimes at 3700 rpm I am doing 24 mph and 2.2 mpg and sometimes 28 and 3 mpg.

This is with my new prop.

My old stock prop was 3500 rpm, 24 mph, and 2.25 mpg on average.

Now, how do I get a free E-tec to try?

posted 09-12-2008 02:20 PM ET (US)            

Actual, or as close as I remember:

Cruise with Johnson 225 was about 24.5 kts (28.8 mph) at 4000-4200 rpm (can't remember) and I hoped (wished) for 2 nmpg (2.3 mpg).

Cruise with 225 Optimax is now 29.3 kts (33.7 mph) at 3750 rpm and about 3.2 nmpg (3.7 mpg). Longest FULLY LOADED camping trip 45 gallons for 135 nm = 3.0 nmpg (3.45 mpg)at 3900 rpm.

Top speed went from 41 kts (47.15 mph) to 43.0 kts (49.45 mph).

posted 09-12-2008 08:56 PM ET (US)            

Again, when you want to set up a comparison, it is important to keep conditions similar. It is hard to compare absolute values when there are very significant differences in the situations. Saltwater gives better performance than freshwater. Cold water gives better performance than warm water. Cool dry air gives better performance than hot and humid air. One boat's hull runs differently than another. One fuel flow meter reads differently than another.

What I can tell you about my test is that with the same boat, the same instruments, the same load, the same driver, the same water (Lake Huron and Lake Michigan--they're connected), and about the same weather (somewhat hotter in August than July) I found speed increases and fuel economy increases with the E-TEC motor. The speed increase was off the chart, and the fuel economy increase was just a bit better than predicted.

posted 09-12-2008 11:07 PM ET (US)            

You sum it up well.

My old 1989 225 Johnson DID NOT HAVE a flow meter - it was a guess based on approximate mileage and gallons used - room for error.

The 225 Merc Optimax has a flow meter - which seems accurate (but not calibrated) with gallons used and miles run.

I've got plenty of cold salt water and cool WET air!

Also, canvas makes a difference - I'd guess at least a few percent. I used to rarely use mine and you use yours all the time. Regardless, the new technology engines are great!

Putting the boat away for the season this weekend.

The weather has been bad (cold & wet, in fact 4th coldest on record) and the fishing has been bad. Most summers I run without my canvas 90% of the time. This summer the canvas has been up 100% of the time and it's rained 90% of the time! This global cooling is becoming a problem.

posted 09-13-2008 02:56 PM ET (US)            

Well......hmmmmm.......this is really odd.

I surely don't doubt Jimh's ability to perceive things. However, I would like to analyze this a little. Using accepted princples of mechanical engineering and physics.

Lets start with some basics.

When the "propeller load" changes, as it does when the hull resistance changes, the engine either (a) increases torque output, or (b) slows down.

How can an engine increase its torque output? Jimh suggests that it has something to do with "direct injection." This does not really make sense, however.

Torque is produced by the burning of fuel/air mixture in the combustion chamber. Generally the more dense the mixture the greater the combustion pressure and the greater the push on the piston, resulting in more torque.

However, I said "dense" not "rich." Air and fuel must be in proportion, roughly 14:1. Injecting more fuel, without more air, does not do much but cause a overly rich mixture, causing torque to fall off.

So, the only way to increase torque is to increase manifold pressure and let in more air, and also let in more fuel to correspond.

How does the new engine automatically let in more air when the boat goes up on a wake? It is certainly *possible* to design an engine that has autothrottle, and automatically increases throttle setting (letting more air in) to compensate for increased torque demand. Stationary engines often hold set RPM automatically, for example.

However, I have never heard that outboards do this. Certainly, all the other ones I have driven or heard about do not. Optimaxes behave like normal outboards in that respect. They certainly don't have autothrottle or governed RPM. Nor do automobiles with "direct injection", which behave, I would add, exactly like carburated cars on hills, i.e. they don't "hold" RPM any better going uphill (without cruise control, which is, of course, autothrottle.)

This is not to doubt Jimh's observations.

posted 09-13-2008 03:33 PM ET (US)            

These engines can and do produce power in ways that old school 2 strokes can not. The atomisation method of the fuel is also important to the production of power.

If your goal is to glean info from this site then read the already posted info instead of proposing theory. And old theories at that. Science, building and testing changes things taken for truth.

Len

posted 09-13-2008 04:10 PM ET (US)            

I do know that my old carburetor Yamaha motors would hunt up and down in speed in response to load changes, and you had to work the throttle in response to maintain boat speed at a constant. The 225 V6 carburetor motor is better, but it still will run up and down in engine speed, especially in a turn. The E-TEC just runs at the speed you set on the throttle. If you go into a turn, it doesn't begin to drop. It could be something as simple as centrifugal force affecting the fuel in the carburetors. I really don't know. And I really don't care.

[Extended my remarks here: Perhaps I should have written "computer-controlled direct-injection" instead of just "direct-injection" as the control system is probably more influential than the fuel induction system. Also, I notice the same sort of behavior in my cars. When I am driving and the engine has a lot of reserve power, when we approach a grade the engine will pull the car right up the grade without any more throttle. But if the engine does not have much reserve, if it is running near is maximum, when you reach the grade you have to give it more throttle to ascend the grade. I have also seen the same thing in my truck when hauling the boat. If I reach the grade when the engine is running in its power band, say around 2,700-RPM, it will usually ascend the grade without slowing down. If I hit the grade with the engine below its peak power band, say 2,400-RPM, then as soon as the truck is on the grade the engine will begin to slow down from the new load, and I have to give it much more throttle to maintain speed. I think the difference is the amount of reserve power the engine has. In the case of the E-TEC 250 H.O., it seems to have plenty of reserve power when at typical 25-MPH cruise, so when the load momentarily increases, it does not drive the engine speed down.]

My presentation here is simple: I used the same boat, the same instruments, the same gear, the same loading, and the same conditions. Then I tell you the difference in the speed and the fuel economy. It is really rather straightforward.

posted 09-13-2008 04:27 PM ET (US)            

The fundamental principle of my test is that the only variable here is the motor, and everything else is the same or closely controlled. If you want to make comparisons or hypothesis about other boats, with other motors, in other conditions, at other temperatures, with other instruments (or no instruments at all) taking measurements, you are welcome to do so, and people have been making up these comparisons for years. I just don't think these comparisons are significant to my test. I am going to reprint the opening paragraph of the article so that it can reframe the discussion here:

quote:

---

There are many reports about engine performance, but usually they are stand-alone reports, that is, they just report the performance of a motor on a boat. They don't offer much comparative information. When there is comparative information it is usually provided in the context of two motors run on two boats. You hope the boats are identical, because if they're not, the comparison is flawed. Here is a report about two motors compared on the same boat. This is somewhat unique. The boat is my boat, and I have collected a lot of data about how it performs with two different engines. This removes the boat as a variable that can explain any variation in performance between the two motors.

---

posted 09-14-2008 05:16 PM ET (US)            

New Engine: When to Buy
http://continuouswave.com/ubb/Forum1/HTML/010777.html

That article and the follow-on discussion resulted in the creation of a Excel spreadsheet that embodied the concepts into a very handy interactive tool:

Engine Cost Analysis Spreadsheet
http://continuouswave.com/ubb/Forum1/HTML/010848.html

posted 09-15-2008 12:08 PM ET (US)            

However, I have looked closely at the ETEC literature, nothing in any ETEC literature, or any marine literature at all, suggests it has this feature. In fact, implementation of "automatic autothrottle" set to whatever the throttle lever is at, would be very troublesome. More on that below.

Professional ski boats have an autothrottle feature that works like a car cruise control. It is not particularly hard to do. You select a speed and the throttle is moved to keep the speed.

How-ev-er, I want you to understand, it has absolutely nothing to do with "direct injection" or "computer controlled direct injection." True, computer engines set *idle* speed by computer, and can do this because at idle the throttle is *closed* and air is regulated through a separate orfice.

But off idle, fuel alone cannot regulate power output. It takes AIR. And the ETEC has a simple throttle butterfly for air regulation. There is absolutely no indication that the computer has control of the throttle.

Furthermore, it would be impossible to implement as you suggest. Lets think closely about this. Assume for purposes of argument the ETEC has some kind of computer throttle that holds RPM to whatever it is (when? at the time you move the throttle?)

So you push the throttle forward from idle. Lets assume you push it all the way to WOT> The RPM come up, but the boat has not planed. So the RPM go to like 3200 while the boat goes into transition. Normally of course, the RPM will build up as the boat increases speed. But the "autothrottle" will be holding RPM, remember? So how can the RPM increase without moving the throttle.

My point is, if the autothrottle works to keep RPM constant with increasing load, it would work the same in the other direction, keeping RPM from increasing under decreasing load.

posted 09-15-2008 12:36 PM ET (US)            

Why not start a new thread using your last post so as not be derail and dilute Jim's great repowering report?

I'll try to explain the system in some detail that may help with your understanding how the EMM "runs" the motor.

posted 09-15-2008 12:47 PM ET (US)            

Your comments on trucks with "reserve power" going up hills without slowing down are worth mentioning.

"Reserve" power means power (torque, actually) not used on level ground but used going up a hill. Makes sense.

So on level ground, the throttle regulates airflow, and the airflow is such that a balance is maintained between drag and thrust. Going up a hill (without cruise control), the balance is disturbed. You need more torque to maintain the speed, i.e. the new equilibrium. How do you get it? By increased airflow, and fuel to match.

Something needs to move the throttle. Either your foot, or a cruise control. Thats the end of the story.

Has nothing to do with fuel injection. F/I cars slow on hills just like carburated cars.

So, your observations are interesting but perhaps the torque response to a very slight foot movement is so robust that you are not aware of it.

On the ETEC, remember also that if an engine is set up with autothrottle, you need a "pickle" switch to turn on RPM (or speed) hold. For reasons I expressed above, you can't just connect an autothrottle to the throttle lever. It would prevent normal engine operation.

But you should look at some basic IC engine texts, or talk to the ETEC people if this is still unclear.

By the way, the ETEC literature shows nothing at all unusual in its direct injection. Lorenz coils are used to inject calibrated streams into the combustion chamber. The engine does indeed use a throttle position sensor (TPS) to help decide how much fuel is proper under the circumstances, but the engine does NOT move the throttle by itself.

posted 09-15-2008 03:05 PM ET (US)            

I own an Optimax and it has nothing of the sort.

If the throttle "holds" an RPM, does that mean if you trim the engine out it won't be able to increase RPM either?

I usually know when people are frustrated and out of their intellectual depth they start calling names.

Thus I won't return the insult.

posted 09-15-2008 03:57 PM ET (US)            

Try to read through my "layman" speak, since I don't have the complete grasp of vocabulary in this area - but I think I have an understanding of the idea/concept. I believe that the new motors either have a greater reserve of torque, or they *somehow* do not struggle as much when presented with the significant change in resistance as when a hull runs through seas. It is not an "autothrottle", since the RPM's will jump when you exit the water (I call this "barking" the props - it's that brief moment when the exhaust hub is exposed and the apparent engine noise is considerably higher as the blades freewheel and the exhaust runs uninhibited into air instead of water...and the blades spin up quickly). Likewise, the motor will increase RPM at a given throttle (binnacle control) setting when you trim the motor.

What it doesn't do, unlike previous motors I've owned, is "bog down" when going into or climbing the backside of a wave. I can set the binnacle control at a speed I like, and the motor will not "drop down, or hunt up" to where it's happy - it runs where I "tell" it to - I set the control and then match the twin...when I hit waves, the motor doesn't "uuhh" grunt in the RPM like the old carbed motor did...it just pushes straight through.

I believe that is what JimH is referring to, as I experience it on my E-TEC motors as well. I don't know or really care about the engineering reason behind the phenomenon (I know you do though!)...I just like it very much as a characteristic of the final product.

Cheers,

Dave

PS - Intellect on it's own doesn't have a lot to do with expertise in a given area - because one person is an expert in a given subject does not mean that he/she is more intelligent than someone for whom the subject matter is foreign.

Just a point of clarity.

posted 09-15-2008 06:44 PM ET (US)            

Best economy cruise speed (provided I can trim it out reasonably well in calm water) is 3500 RPM at 26-27 MPH burning 8.0 gph (readings from Northstar F210 fuel flow meter). Fuel economy is 3 MPG or better between 18 and 36 mph.

As far as calibration of the fuel flow meter, when I filled it up with between 60-70 gallons on 4 separate occasions this summer, the flowmeter usually read about 1-2 gallons less than what I actually pumped in. This inaccuracy is probably due to the very low flow rate at idle when I leave and return to my marina for 1 mile each trip (typically .2-.3 GPH at idle).

posted 09-15-2008 11:27 PM ET (US)            

I totally agree. My point was (a) all motors slow down unless they have autothrottle; and (b) it has nothing to do with fuel injection.

How much RPM will an engine lose climbing a wake for example?

When you increase the drag, the engine slows because it cannot produce the added torque to keep the speed, without an increase in air. And there is no autothrottle so no more air.

So the engine slows, and the boat slows. Soon it comes to a new equilibrium that the engine can manage with the torque it has.

Now if you slow an engine and keep the throttle constant, what happens to the torque? Well, it depends. If you are already operating at best torque RPM, then the torque falls, and the boat slows even more. How much it slows depends on the partial throttle torque curve, and the hull resistance curve.

The new engine probably has a flatter torque curve, which is indeed a function of its EMS, its combustion chamber design, its port and ignition timing, its fuel timing, and other things.

Thus it slows less on a wave.

My point was not to jump to easy explanations. All ungoverned engines slow with increased load. Engines with flat partial power torque curves (not "reserve power" --thats different) slow less (depending on the hull of course).

posted 09-21-2008 12:03 PM ET (US)            

I took some measurements of the gear case of the older 225 V6 and the new 250 H.O., and, to my surprise, I found that the propeller shaft height on the new motor was actually higher than on the old motor. Recall both were mounted in the lowest position on the transom of the Whaler Drive. My initial feeling was the L2 gear case might put the propeller down a bit lower, but as it turns out the L2 puts the propeller shaft about "one-hole" higher (or about 0.75-inch). I have added this information to the reference article, along with some figures I computed for the propeller SLIP.

The REBEL propeller gave no sign of blowing out, even with the rather elevated mounting. Giving the Whaler Drive credit for about "two-holes" of elevated mounting, and giving the L2 case credit for about "one-hole" of elevated mounting, I would judge the installation now has the engine mounted at "three-holes up" as a comparative indicator to a normal notched transom Boston Whaler boat.

The REBEL propeller shows the usual tapering SLIP values, ending up at around 10-percent SLIP at maximum speed. As I mention in the article now, a SLIP of 10-percent is about typical for a single engine propeller on a heavy boat on plane. I have seem some slightly lower figures, but these may have been influenced by the pitch of the propeller being understated.

posted 09-24-2008 11:16 PM ET (US)            

I added two graphs and two photographs, along with quite a bit of narrative, to the original article as an addendum about this propeller. Rather than repeat all of that here, I will ask readers to indulge me by revisiting the original article to see and read the added remarks.

posted 09-25-2008 12:51 AM ET (US)            

In a nut shell, the Cyclone yield the same peak fuel mileage but over a slightly broader RPM range. Do I have that correct?

I do not know if your old motor will ever be going back on your boat but if it does I would very much like to see some testing done with that motor and one or both of the propeller models you have tried on the E-TEC.

posted 09-26-2008 09:51 AM ET (US)            

Weight = 5,400-lbs
Speed = 30-MPH
Fuel Economy = 2.65-MPG

Using Crouch's Speed Calculator to deduce the horsepower, with a hull factor of 180 we get 150-HP.

Now we can compute a BSFC figure:

30-miles/1-hour x 1-gallon/2.65-miles = 11.3 gallon/hour

11.3-gallons/hour x 6.25-lbs/gallon = 71-lbs/hour

BSFC = 71-lbs/hour x 1/150-HP = 0.47 lbs/HP-hour

This figure is a bit higher than the anticipated target BSFC of 0.45. The variance may be likely related to measurement errors or erroneous assumption. As I already expressed, the fuel flow rate measurement is known to be in error and overstates fuel flow. This measurement error will contribute to the BSFC being too high. Also, the exact horsepower being used to produce the observed boat speed is only inferred from an assumption of the hull factor constant and Crouch's estimator. This is also subject to error. The imputed BSFC, 0.47, is in good agreement with the anticipated value, 0.45, and allowing for the fuel measurement error, the calculation seems reasonable. A BSFC value for direct-injected two-cycle motors is believed to be in this range.

posted 09-27-2008 10:15 PM ET (US)            

Try a 19 or a 21 and see it improve, I bet.

posted 09-28-2008 11:55 AM ET (US)            

Since my boat is about the same length but does not weigh nearly as much as yours my top speed reached 56-MPH without any special changes and I do not really care much about speed. At 450-RPM I cannot hear nor feel the engine running when I am at the cockpit. I have to look down at the Tachometer to check if engine is running. Did you have similar experiences with the sound?

posted 09-28-2008 12:37 PM ET (US)            

I had the cowling off this weekend looking at the cables, and I found the hold-down screw at the engine end which holds the throttle cable had loosened itself. This may be a sign of the vibration. There might be an odd resonance in my set up that is creating this. I think on a long-term basis it could be worked out with new throttle cables--I have had that in mind anyways as the current ones could be a foot or two longer in order to permit them to lay more comfortably in the rigging. With the Whaler Drive configuration the cables have to make a fairly sharp bend as they pass through the transom rigging tube and then bend downward to clear the lazarette locker.

posted 09-28-2008 12:56 PM ET (US)            

These results should more clearly show the difference between the E-TEC 250 H.O. and the 225-HP V6, as the only thing changed is the engine. The boat and propeller remain the same. I am afraid the test conditions could not be exactly duplicated, as the boat weight was lighter, the air temperature was cooler, and water was generally smoother than in the weeklong period when the data was collected for the 225-HP V6. These may tend to favor the E-TEC a bit in this comparison. However, even with perhaps a slight tilt in favor of the E-TEC, the results are still impressive.

The E-TEC averaged 2.51-MPG over a 59.8-mile day of boating and 23.8-gallon of gas consumed (and, by the way, we were generally hauling, going either at idle or 30-MPH). This compares to the 225-HP V6 which averaged 1.72-MPG over 262.5 miles of boating and 153-gallons of (very expensive Canadian) gasoline (where we tried to run at the best possible fuel economy at all times). The fuel economy of the E-TEC in miles-per-gallon was 46-percent better.

To put fuel economy in perspective, consider that a boat that gets 2.51-MPG uses 0.398-gallons per mile, and a boat that gets 1.72-MPG uses 0.581-gallons per mile. In my recent 262.5 mile cruise, if I had been running the E-TEC motor I would have used 104.6-gallons of gasoline, a savings of 48.4-gallons. Since we were buying gasoline that week at an average price of $5.20/gallon, the E-TEC would have saved us over $250. If I used my boat like that every week, the fuel savings would accumulate quite rapidly, and the new motor could pay for itself in just a few years.

posted 10-08-2008 01:07 AM ET (US)            

I will go into more detail in an addendum to the original article, but the executive summary is this: the I-Command fuel flow data showed significantly different flow rates than the existing Navman fuel flow instrument. The trend was that the Navman under-reported fuel flow at the very low flow rates, and then over-reported it at the higher flow rates. The error is more significant at the high flow rates, and there the Navman was showing the fuel flow to be more than ten percent higher than actual. As a result, the E-TEC delivers fuel economy of 3- to 3.1-MPG in the normal cruising speed range as reported by the I-Command data. These figures are completely in-line with my general feeling about the calibration error in the Navman, and fit with my other observations on the actual fuel being used as determined by tank level.

posted 10-08-2008 03:49 AM ET (US)            

Is the I-Command system 100% accurate?

Have you calibrated your Navman 3100?

posted 10-08-2008 08:53 AM ET (US)            

The I-Command data about fuel flow comes from the engine EMM, so the engine is measuring itself. There is not a fuel flow transducer. I believe the fuel flow is calculated based on the throttle setting and time. The engine knows with extreme precision how much fuel it is injecting with each injector for each cylinder at every throttle setting. It accumulates this fuel volume data, integrates it over time, and presents a reading of fuel flow in gallons per hour. I don't know the absolute accuracy of this technique, and of course there is a bit of suspicion that the data might be skewed to make the engine look better than it really is. But there is a sound basis for the technique.

In several engine comparisons which were published in magazines, the test procedures allowed some of the engines to compute their own fuel economy while other engines in the test were measured with external fuel flow devices. I think this is a poor test technique, and particularly so when trying to compare engines whose fuel economy is expected to be very similar.

posted 10-08-2008 12:22 PM ET (US)            

It may or may not be.

The internal I-command computation is not based on "actual" fuel flow, but on computed fuel flow. In other words, the engine computer is telling you how much fuel it ordered, not how much was delivered. Since the injectors are not perfect, the actual delivery may be other than the computed delivery. Plus, an algorithm, unknown to the public, is needed to convert from the internal units to gallons used or flow rates.

However, the paddlewheel sensors in the other instrument are certainly not perfect. Especially at low fuel flow rates, static friction in the paddlewheel causes underreporting of flow.

Both should be compared with refueling data, i.e. gallons bought from the pump versus total fuel used as displayed.

Of course, refueling data is not perfect either. Whether a tank is "full" depends on its attitude and how patient you want to be in filling. The temperature of the fuel affects its volume in the tank. The calibration of the fuel delivery system at the gas station is subject to legal regulation, but how accurate it is I have no idea.

posted 10-08-2008 12:31 PM ET (US)            

It is my understanding that fuel comsumption numbers are coming from each injector as it fires. These injectors are calibrated/measured by milliseconds of on time and that data is programmed into the EMM when new or replaced. The software for these engines allow you to change injectors by entering the calibration number for the new injector.

The lenght of injection is controlled by the EMM depending on demand and engine load. Oh, and temperature, barimetric pressure. Have you noted on the I-Command gauge that barimetric pressure is a variable that can be diplayed.

This would make it easy for this data to be calculated from the injector data by adding the volume of each injection during the last minute.

Can you part with the E-TEC? You sound happy.

posted 10-08-2008 02:45 PM ET (US)            

Also, on the 2008 E-TEC engine the injectors have over 30 coefficients by which their flow rate is computed and adjusted by the EMM. The EMM knows precisely how much fuel it is going to use because that is how it keeps the exhaust emission so clean--it precisely controls the fuel and air mixture. I have to imagine that the algorithm to integrate that flow over time and produce a figure for gallons per hour would not be prone to error.