Suspicion of False Testing by Mercury and Yamaha

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Author Topic:   Suspicion of False Testing by Mercury and Yamaha

L H G posted 08-06-2013 02:04 PM ET (US)
Some here consider Mercury's Optimax testing to be suspect, so would this apply to this Yamaha report ?
Peter posted 08-06-2013 04:16 PM ET (US)
Yamaha needs to do something to distract from the bad publicity they are getting on the 3.3L V6 4-stroke corrosion problems.
martyn1075 posted 08-06-2013 05:12 PM ET (US)
I hear about this corrosion stuff what is happening to these long lasting engines that seem to sell so many probably more than any other engine maker out there.
Where do they seem to be rotting out?
Martyn
Tom W Clark posted 08-06-2013 08:17 PM ET (US)
Big deal. The motor is only three years old.
It should not be surprising that a three year old outboard motor is still running.
jimh posted 08-06-2013 09:06 PM ET (US)
What is the basis to claim this test information is false? Or that OptiMax test data is false.
Perhaps you can lay out your thesis more clearly. It makes no sense. Why does this report from Yamaha have anything to do with Mercury?
Also, I deleted some ridiculous claims also made in the initial article. I am not interested in publishing pure nonsense.
prj posted 08-06-2013 09:16 PM ET (US)
[Changed topic to begin to discuss this article's title and deletions made to the original article which removed wildly speculative statements not implied in any way in the Yamaha performance report--jimh.]
jimh posted 08-07-2013 12:13 PM ET (US)
The report which is linked in the initial article, and whose credibility is made the central theme of this discussion, is a report of engine test data conducted by Yamaha on one of their engines. This particular engine was a 2005 engine which had been in commercial operation and racked up 8,700-hours of service.
Let me first comment on the hours of service. I find the 8,700-hours of service without any mention of a major repair or overhaul to be remarkable. I understand that other readers may have less praise for such a report, but in my opinion 8,700-hours of operation without a major repair is a significant achievement.
The principal point of the test results is to convey the durability and endurance of the Yamaha engine. Test data using the old engine was obtained, and a comparison is made to test data using a new engine on the same boat. The results are very similar. Data is reported for time to plane (or acceleration), maximum speed, and fuel economy (at unspecified load or speed). In the case of acceleration and top speed, the variation between old and new is very small and probably statistically insignificant. There is a slightly greater variation in fuel economy, but it is hard to judge if there is a statistical significance to the difference.
Regarding the test data and how it was gathered, the data seems to have been collected in the best possible method. The same boat was used in both tests, and I assume the same methods for measuring and collecting the data was used. This represents the best method, in my opinion, for comparison of engines. Using two engines on one boat, obtaining all the data in the same way, and conducting the tests very close in time so that other environmental factors are the same is the best method. Comparison of results like this are, for me, much more valid that comparisons which are often suggested. In some prior comparisons it has been suggested that results obtained by different engines, on different boats, measured by different instrumentation, by different testers, on different bodies of water, at different times should be held as strictly comparable and reliable. When people have made assertions like that, I tend to find little validity in the comparisons due to the many opportunities for other variables besides the engines to influence the outcome. In the Yamaha method of comparison, only the engine changed. Almost all other factors remained unchanged. For that reason, I tend to find the Yamaha test results to be believable. I do not find any particular reason to assert a claim of false testing to the Yamaha results that are the topic of discussion here.
Binkster posted 08-07-2013 09:48 PM ET (US)
Was the outboard owned by the water taxi service, or was it owned and donated by Yamaha and serviced by the factory every month or maybe even weekly?
Remember the endurance test put on by Mercury with their first inline six in the late 50's at Lake X. How many thousands of nonstop miles was that? I forgot. A friend was a test driver, and said it was a crock. The engines were repaired all the time. They even knew how to take the seals off the block and replace them so they looked original. Actually it mentions this in Carl's book "Iron Fist".
rich
jimh posted 08-08-2013 12:17 PM ET (US)
I don't find Yamaha's interest in this engine to be unusual or suspicious. Manufacturers of engines often like to find instances of their products in the field which have accumulated very high hours of operation. For example, a few years ago at the North American International Auto Show, the auto manufacturer SAAB was exhibiting a 1989 SAAB that had been driven by its original owner over 1,000,000-miles using its original engine.
http://www.jsonline.com/business/29181064.html
jimh posted 08-08-2013 12:30 PM ET (US)
In general, I am not particularly worried about falsified information from outboard engine tests conducted by manufacturers. Most of the time the method of testing is well known and the tests are quite open and transparent. For example, when a test is recorded by motion picture and sound, it is quite clear how the test was conducted. I am more skeptical of carefully selected data points in which one manufacturer compares his product to another but gives very little information about the test conditions, and does not include any other data, just the single point. It not hard to pick particular data points in a series of tests that make for very favorable comparisons, but if the all of the other data is omitted, the weight given to a single data point must be limited, at least it should be by rational readers and independent thinkers.
In the present environment of extremely easy access to distribution of information, it is hard to keep a lid on secrets, and a deception, like the one alluded to in a test by Mercury (see above), would be hard to maintain in the modern era. Someone would leak the secret.
Also, there seems to me more scrutiny by federal regulators about misleading or deceitful advertising, and a company would be foolish to risk the criminal charges and the public humiliation that would result if a deception were revealed. It is probably more cost effective to invest in a better product than to try to cheat in the advertising.
Boat test data from companies like Boston Whaler are, in my opinion, quite reliable and likely to be representative of the boats, motors, and propellers tested. Those test results include much data about the test conditions, often including environmental data about temperature and weather.
On the other hand, when manufacturer A comes out with a giant graph with an exaggerated scale and plots a single data point in which there is a claim of a difference with competitor B by 40-percent, I tend to ignore that as marketing hyperbole. I believe that if there were truly an honest 40-percent difference in A and B, this would soon become extremely obvious to the boating public, and the model with a 40-percent improvement would soon drive the competitors out of business.
andygere posted 08-09-2013 04:31 PM ET (US)
I suspect that the vast majority of those 8700 hours are at idle or very low speed. With proper maintenance, it is not terribly shocking that the motor is still performing well.
jimh posted 08-10-2013 07:56 AM ET (US)
A good example of how manufacturers perform testing of their own products and present the test results is provided by Ford. When Ford introduced a new engine for their F-150 truck, they conducted a lengthy and very public testing of the engine. First a production line engine was selected at random, Then they ran the test engine in their laboratory under very heavy and grueling test conditions. Then they installed the test engine in a actual F-150 truck. The truck was then driven in an extreme manner. Finally, the test engine was removed, disassembled, and critical mechanical tolerances and wear measured in front of a live audience of automotive journalists at a major trade show. This entire process was recorded in motion picture and sound, and edited into a lengthy presentation. (See http://www.youtube.com/watch?v=8tEqwXrqzH4 and five more segments.)
This method of testing and presentation of the test results by Ford for their engine established the credibility of the testing and the results.The use of motion picture and sound recording of engine tests is becoming an important tool in communicating engine test results. Imagine the difference in communication of data if Ford had done all that testing in secret, then produced a few simple bar charts or graphs showing one or two data points, and omitting all details of the tests and the testing process. In the present day, if you want to remove skepticism and suspicion, perform the tests with plenty of witnesses and record the results with motion picture and sound.
martyn1075 posted 08-10-2013 01:36 PM ET (US)
I find the whole system to be a believe it or not scenario with people who actually own the boat and motor(s) Presenting it in the clearest manner possible sometimes still isn't enough for some to believe. If someone ask you to present rpm gph mph and you do so in live video in differnet scenerios should that not be enough to at least give an average? Well of course one would think so, its right there in front of your face. There are easy calculations to give you an average mpg performance based on live data.

However when the facts don't come out they way one thought other things come into play. GPS isn't working or wind or the video was cut. Or you must of made changes in speed to achieve that. If someone is skeptical they will always be skeptical. The skeptic becomes the diver or the vessel owner rather than just trusting the one one knows the boat best which is why I always say a believe or not scenario.
These little games get introduced maybe we should consider movie motion and sound.
Martyn
silentpardner posted 08-11-2013 12:21 PM ET (US)

quote:
I hear about this corrosion stuff what is happening to these long lasting engines that seem to sell so many probably more than any other engine maker out there.
Where do they seem to be rotting out?
Martyn
Could someone please answer this question, I too am curious. Please give me a fact based reply with some documentation if possible. I am not interested in religious beliefs here, just documented fact.
Peter posted 08-11-2013 01:16 PM ET (US)
Just one of many links discussing the problem www.boatus.com/magazine/2012/october/Yamaha-F225-Corrosion-Complaints. asp .
Yamaha sold alot of F225s before the problem surfaced. If you have one on your transom they make the boat harder to sell.
silentpardner posted 08-11-2013 04:05 PM ET (US)
Interesting, I just checked out a Whaler 27 with a pair of these engines from 2003...no problems at all, they have 700 hrs or so on them. I wonder why it appears to be a problem ONLY with the 225's and not the entire line of the same motors? They all were built the same way I thought...
onlyawhaler posted 08-12-2013 11:32 AM ET (US)
According to the article link above, this issue is specifically pointing towards the F225, years 2000-2004 only. Its exhaust related and affects the oil pan and other areas once the rust has gone through. Update kits are about $600 and provide coated parts, but the labor is expensive.
If I am not mistaken, this F225 was the first big 4 stroke in this class offered by anyone. Obviously a learning curve and it doesn't appear to apply to any other models during that time.
Sterling
Onlyawhaler
seahorse posted 08-12-2013 11:54 AM ET (US)
Actually the whole family of F200-225-250 engines are subject to the internal exhaust corrosion, some including 2006 engines have been mentioned.
There are several areas where corrosion occurs in the exhaust areas, but the most common the water/exhaust separation plate. When pinholes develop then grow larger, the engine usually overheats at slow idle but will cool normally at about 1000 rpm. It was this plate that received the special coating in '04 when the cylinder blocks and internal parts were redesigned for 3 star emission ratings. Earlier ones were only 2 star.
Engines on heavier salt-water boats seem more prone to the corrosion issue, especially when marginally over propped which tells me it may be related to higher exhaust temperatures.
Marko888 posted 08-12-2013 12:39 PM ET (US)
Regarding the F225 corrosion issues.
A very good friend of mine is a salmon guide, and his went bad at 3800 hours, and it went exactly as seahorse describes...overheating at idle, no problems at higher RPM. To the chagrin of his dealer, he plumbed a bilge pump into the flushing circuit and ran the bilge pump when idling...it got him through to the end of that season!
jimh posted 08-14-2013 02:04 PM ET (US)
The amount of skepticism expressed with a boat test report is correlated with how far the results of the test differ from the normal outcome or the anticipated outcome. For example, if someone reports that they can propel a boat to a certain speed with an engine of 150-HP, and prior experience is that a boat of that type normally requires 225-HP to reach that speed, we have a rather significant deviation from the expected outcome. The expected outcome is usually based on past testing and on the laws of Physics. When test data is presented that is incongruent with prior outcomes, and when that same test data seems to violate the laws of Physics, I think there is sufficient basis for expression of some skepticism in the test report.
Measurement of test data is prone to variation in accuracy and precision. Some test data is the product of more than one measured process. For example, a test result that gives fuel economy in miles per gallon is a product of two measurements: rate of movement of the boat and rate of movement of the fuel. In each process there is some error. When the two measurements are multiplied together, the errors can become additive. If the errors in measurement are skewed in the right direction, for example, if the boat speed measurement overstates the boat speed and if the fuel flow measurement understates the flow rate, then the computed fuel economy can be in error by an amount greater than either measurement's error. Let me demonstrate.
Suppose a boat goes exactly 1-MPH and consumes exactly 1-GPH. We have a true fuel economy of 1-MPG. If we install instruments and measure the speed and fuel flow rate, we might have a measuring error of ten-percent in each measurement. We might measure the speed as being 1.1-MPH and the fuel flow rate as 0.9-GPH. With this data we compute an MPG of 1.22-MPG. We now have a 22-percent error in the data, even though our measurements were accurate to 10-percent.
Suppose the measured values are in error in the opposite direction. We might measure the speed as 0.9-MPH and the fuel flow rate as 1.1-GPH. We would compute an MPG of 0.82. We now have a 18-percent error in the data, even though our measurements were accurate to 10-percent.
Next we compare the two computed values: 1.22-MPG and 0.82-MPG. The actual value of fuel economy in each case was the same, 1.0-MPG, yet we can now see a variation of 0.4-MPG in the measured results. A variation of this magnitude could be presented by claiming that the boat that measures at 1.22-MPG is getting an improvement in fuel economy of 49-percent compared to the boat boat measured to get only 0.82-MPG. This enormous error in test data has occurred with only a 10-percent error in measured data. The truth is the actual MPG is the same.
Speed measurements are also significantly affected by wind and current. This is such a fundamental concept that it should be understood by all. No measurement of boat speed in which correction or allowance for the influence of current and wind has not been provided can be considered as an accurate measurement.
Measurement of fuel flow is now often taken from data from the engine itself from dynamic engine parameters sent on a NMEA-2000 network. It is often assumed that this data must be perfectly accurate and without any error. However, it is also frequently reported that when this fuel flow rate data is accumulated and integrated over time, the computed volume of fuel used is often significantly different than the actual volume of fuel used.
In any method of measurement and comparison in which different measuring instruments are used to take the measurements, there must be absolute accuracy and calibration of the two measuring instruments, otherwise the data obtained can be influenced by the measuring device. To measure fuel flow rate of two engines, the best method would be to use the same instrument to measure both engines. Using a two different instruments to measure two engines just add another source of error.
There are often comparisons made involving two boats, which, because they are of the same model and make, are assumed to be identical. There is little chance of the boats being identical. Even when two boats are made in the same molds, they may not be identical. Variation in lay-up of the laminate may produce variations in the hull weight and hull strength. One boat may have been sitting on a trailer for 20-years with improper support, and the hull shape may have been distorted. One boat may have been in the water for 20-years and picked up hundreds of pounds of added weight from absorbed water. Variations like this will cause variations to the boat speed.

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Author	Topic: Suspicion of False Testing by Mercury and Yamaha
L H G	posted 08-06-2013 02:04 PM ET (US) Some here consider Mercury's Optimax testing to be suspect, so would this apply to this Yamaha report ?
Peter	posted 08-06-2013 04:16 PM ET (US) Yamaha needs to do something to distract from the bad publicity they are getting on the 3.3L V6 4-stroke corrosion problems.
martyn1075	posted 08-06-2013 05:12 PM ET (US) I hear about this corrosion stuff what is happening to these long lasting engines that seem to sell so many probably more than any other engine maker out there. Where do they seem to be rotting out? Martyn
Tom W Clark	posted 08-06-2013 08:17 PM ET (US) Big deal. The motor is only three years old. It should not be surprising that a three year old outboard motor is still running.
jimh	posted 08-06-2013 09:06 PM ET (US) What is the basis to claim this test information is false? Or that OptiMax test data is false. Perhaps you can lay out your thesis more clearly. It makes no sense. Why does this report from Yamaha have anything to do with Mercury? Also, I deleted some ridiculous claims also made in the initial article. I am not interested in publishing pure nonsense.
prj	posted 08-06-2013 09:16 PM ET (US) [Changed topic to begin to discuss this article's title and deletions made to the original article which removed wildly speculative statements not implied in any way in the Yamaha performance report--jimh.]
jimh	posted 08-07-2013 12:13 PM ET (US) The report which is linked in the initial article, and whose credibility is made the central theme of this discussion, is a report of engine test data conducted by Yamaha on one of their engines. This particular engine was a 2005 engine which had been in commercial operation and racked up 8,700-hours of service. Let me first comment on the hours of service. I find the 8,700-hours of service without any mention of a major repair or overhaul to be remarkable. I understand that other readers may have less praise for such a report, but in my opinion 8,700-hours of operation without a major repair is a significant achievement. The principal point of the test results is to convey the durability and endurance of the Yamaha engine. Test data using the old engine was obtained, and a comparison is made to test data using a new engine on the same boat. The results are very similar. Data is reported for time to plane (or acceleration), maximum speed, and fuel economy (at unspecified load or speed). In the case of acceleration and top speed, the variation between old and new is very small and probably statistically insignificant. There is a slightly greater variation in fuel economy, but it is hard to judge if there is a statistical significance to the difference. Regarding the test data and how it was gathered, the data seems to have been collected in the best possible method. The same boat was used in both tests, and I assume the same methods for measuring and collecting the data was used. This represents the best method, in my opinion, for comparison of engines. Using two engines on one boat, obtaining all the data in the same way, and conducting the tests very close in time so that other environmental factors are the same is the best method. Comparison of results like this are, for me, much more valid that comparisons which are often suggested. In some prior comparisons it has been suggested that results obtained by different engines, on different boats, measured by different instrumentation, by different testers, on different bodies of water, at different times should be held as strictly comparable and reliable. When people have made assertions like that, I tend to find little validity in the comparisons due to the many opportunities for other variables besides the engines to influence the outcome. In the Yamaha method of comparison, only the engine changed. Almost all other factors remained unchanged. For that reason, I tend to find the Yamaha test results to be believable. I do not find any particular reason to assert a claim of false testing to the Yamaha results that are the topic of discussion here.
Binkster	posted 08-07-2013 09:48 PM ET (US) Was the outboard owned by the water taxi service, or was it owned and donated by Yamaha and serviced by the factory every month or maybe even weekly? Remember the endurance test put on by Mercury with their first inline six in the late 50's at Lake X. How many thousands of nonstop miles was that? I forgot. A friend was a test driver, and said it was a crock. The engines were repaired all the time. They even knew how to take the seals off the block and replace them so they looked original. Actually it mentions this in Carl's book "Iron Fist". rich
jimh	posted 08-08-2013 12:17 PM ET (US) I don't find Yamaha's interest in this engine to be unusual or suspicious. Manufacturers of engines often like to find instances of their products in the field which have accumulated very high hours of operation. For example, a few years ago at the North American International Auto Show, the auto manufacturer SAAB was exhibiting a 1989 SAAB that had been driven by its original owner over 1,000,000-miles using its original engine. http://www.jsonline.com/business/29181064.html
jimh	posted 08-08-2013 12:30 PM ET (US) In general, I am not particularly worried about falsified information from outboard engine tests conducted by manufacturers. Most of the time the method of testing is well known and the tests are quite open and transparent. For example, when a test is recorded by motion picture and sound, it is quite clear how the test was conducted. I am more skeptical of carefully selected data points in which one manufacturer compares his product to another but gives very little information about the test conditions, and does not include any other data, just the single point. It not hard to pick particular data points in a series of tests that make for very favorable comparisons, but if the all of the other data is omitted, the weight given to a single data point must be limited, at least it should be by rational readers and independent thinkers. In the present environment of extremely easy access to distribution of information, it is hard to keep a lid on secrets, and a deception, like the one alluded to in a test by Mercury (see above), would be hard to maintain in the modern era. Someone would leak the secret. Also, there seems to me more scrutiny by federal regulators about misleading or deceitful advertising, and a company would be foolish to risk the criminal charges and the public humiliation that would result if a deception were revealed. It is probably more cost effective to invest in a better product than to try to cheat in the advertising. Boat test data from companies like Boston Whaler are, in my opinion, quite reliable and likely to be representative of the boats, motors, and propellers tested. Those test results include much data about the test conditions, often including environmental data about temperature and weather. On the other hand, when manufacturer A comes out with a giant graph with an exaggerated scale and plots a single data point in which there is a claim of a difference with competitor B by 40-percent, I tend to ignore that as marketing hyperbole. I believe that if there were truly an honest 40-percent difference in A and B, this would soon become extremely obvious to the boating public, and the model with a 40-percent improvement would soon drive the competitors out of business.
andygere	posted 08-09-2013 04:31 PM ET (US) I suspect that the vast majority of those 8700 hours are at idle or very low speed. With proper maintenance, it is not terribly shocking that the motor is still performing well.
jimh	posted 08-10-2013 07:56 AM ET (US) A good example of how manufacturers perform testing of their own products and present the test results is provided by Ford. When Ford introduced a new engine for their F-150 truck, they conducted a lengthy and very public testing of the engine. First a production line engine was selected at random, Then they ran the test engine in their laboratory under very heavy and grueling test conditions. Then they installed the test engine in a actual F-150 truck. The truck was then driven in an extreme manner. Finally, the test engine was removed, disassembled, and critical mechanical tolerances and wear measured in front of a live audience of automotive journalists at a major trade show. This entire process was recorded in motion picture and sound, and edited into a lengthy presentation. (See http://www.youtube.com/watch?v=8tEqwXrqzH4 and five more segments.) This method of testing and presentation of the test results by Ford for their engine established the credibility of the testing and the results.The use of motion picture and sound recording of engine tests is becoming an important tool in communicating engine test results. Imagine the difference in communication of data if Ford had done all that testing in secret, then produced a few simple bar charts or graphs showing one or two data points, and omitting all details of the tests and the testing process. In the present day, if you want to remove skepticism and suspicion, perform the tests with plenty of witnesses and record the results with motion picture and sound.
martyn1075	posted 08-10-2013 01:36 PM ET (US) I find the whole system to be a believe it or not scenario with people who actually own the boat and motor(s) Presenting it in the clearest manner possible sometimes still isn't enough for some to believe. If someone ask you to present rpm gph mph and you do so in live video in differnet scenerios should that not be enough to at least give an average? Well of course one would think so, its right there in front of your face. There are easy calculations to give you an average mpg performance based on live data. However when the facts don't come out they way one thought other things come into play. GPS isn't working or wind or the video was cut. Or you must of made changes in speed to achieve that. If someone is skeptical they will always be skeptical. The skeptic becomes the diver or the vessel owner rather than just trusting the one one knows the boat best which is why I always say a believe or not scenario. These little games get introduced maybe we should consider movie motion and sound. Martyn
silentpardner	posted 08-11-2013 12:21 PM ET (US) quote: I hear about this corrosion stuff what is happening to these long lasting engines that seem to sell so many probably more than any other engine maker out there. Where do they seem to be rotting out? Martyn Could someone please answer this question, I too am curious. Please give me a fact based reply with some documentation if possible. I am not interested in religious beliefs here, just documented fact.
Peter	posted 08-11-2013 01:16 PM ET (US) Just one of many links discussing the problem www.boatus.com/magazine/2012/october/Yamaha-F225-Corrosion-Complaints. asp . Yamaha sold alot of F225s before the problem surfaced. If you have one on your transom they make the boat harder to sell.
silentpardner	posted 08-11-2013 04:05 PM ET (US) Interesting, I just checked out a Whaler 27 with a pair of these engines from 2003...no problems at all, they have 700 hrs or so on them. I wonder why it appears to be a problem ONLY with the 225's and not the entire line of the same motors? They all were built the same way I thought...
onlyawhaler	posted 08-12-2013 11:32 AM ET (US) According to the article link above, this issue is specifically pointing towards the F225, years 2000-2004 only. Its exhaust related and affects the oil pan and other areas once the rust has gone through. Update kits are about $600 and provide coated parts, but the labor is expensive. If I am not mistaken, this F225 was the first big 4 stroke in this class offered by anyone. Obviously a learning curve and it doesn't appear to apply to any other models during that time. Sterling Onlyawhaler
seahorse	posted 08-12-2013 11:54 AM ET (US) Actually the whole family of F200-225-250 engines are subject to the internal exhaust corrosion, some including 2006 engines have been mentioned. There are several areas where corrosion occurs in the exhaust areas, but the most common the water/exhaust separation plate. When pinholes develop then grow larger, the engine usually overheats at slow idle but will cool normally at about 1000 rpm. It was this plate that received the special coating in '04 when the cylinder blocks and internal parts were redesigned for 3 star emission ratings. Earlier ones were only 2 star. Engines on heavier salt-water boats seem more prone to the corrosion issue, especially when marginally over propped which tells me it may be related to higher exhaust temperatures.
Marko888	posted 08-12-2013 12:39 PM ET (US) Regarding the F225 corrosion issues. A very good friend of mine is a salmon guide, and his went bad at 3800 hours, and it went exactly as seahorse describes...overheating at idle, no problems at higher RPM. To the chagrin of his dealer, he plumbed a bilge pump into the flushing circuit and ran the bilge pump when idling...it got him through to the end of that season!
jimh	posted 08-14-2013 02:04 PM ET (US) The amount of skepticism expressed with a boat test report is correlated with how far the results of the test differ from the normal outcome or the anticipated outcome. For example, if someone reports that they can propel a boat to a certain speed with an engine of 150-HP, and prior experience is that a boat of that type normally requires 225-HP to reach that speed, we have a rather significant deviation from the expected outcome. The expected outcome is usually based on past testing and on the laws of Physics. When test data is presented that is incongruent with prior outcomes, and when that same test data seems to violate the laws of Physics, I think there is sufficient basis for expression of some skepticism in the test report. Measurement of test data is prone to variation in accuracy and precision. Some test data is the product of more than one measured process. For example, a test result that gives fuel economy in miles per gallon is a product of two measurements: rate of movement of the boat and rate of movement of the fuel. In each process there is some error. When the two measurements are multiplied together, the errors can become additive. If the errors in measurement are skewed in the right direction, for example, if the boat speed measurement overstates the boat speed and if the fuel flow measurement understates the flow rate, then the computed fuel economy can be in error by an amount greater than either measurement's error. Let me demonstrate. Suppose a boat goes exactly 1-MPH and consumes exactly 1-GPH. We have a true fuel economy of 1-MPG. If we install instruments and measure the speed and fuel flow rate, we might have a measuring error of ten-percent in each measurement. We might measure the speed as being 1.1-MPH and the fuel flow rate as 0.9-GPH. With this data we compute an MPG of 1.22-MPG. We now have a 22-percent error in the data, even though our measurements were accurate to 10-percent. Suppose the measured values are in error in the opposite direction. We might measure the speed as 0.9-MPH and the fuel flow rate as 1.1-GPH. We would compute an MPG of 0.82. We now have a 18-percent error in the data, even though our measurements were accurate to 10-percent. Next we compare the two computed values: 1.22-MPG and 0.82-MPG. The actual value of fuel economy in each case was the same, 1.0-MPG, yet we can now see a variation of 0.4-MPG in the measured results. A variation of this magnitude could be presented by claiming that the boat that measures at 1.22-MPG is getting an improvement in fuel economy of 49-percent compared to the boat boat measured to get only 0.82-MPG. This enormous error in test data has occurred with only a 10-percent error in measured data. The truth is the actual MPG is the same. Speed measurements are also significantly affected by wind and current. This is such a fundamental concept that it should be understood by all. No measurement of boat speed in which correction or allowance for the influence of current and wind has not been provided can be considered as an accurate measurement. Measurement of fuel flow is now often taken from data from the engine itself from dynamic engine parameters sent on a NMEA-2000 network. It is often assumed that this data must be perfectly accurate and without any error. However, it is also frequently reported that when this fuel flow rate data is accumulated and integrated over time, the computed volume of fuel used is often significantly different than the actual volume of fuel used. In any method of measurement and comparison in which different measuring instruments are used to take the measurements, there must be absolute accuracy and calibration of the two measuring instruments, otherwise the data obtained can be influenced by the measuring device. To measure fuel flow rate of two engines, the best method would be to use the same instrument to measure both engines. Using a two different instruments to measure two engines just add another source of error. There are often comparisons made involving two boats, which, because they are of the same model and make, are assumed to be identical. There is little chance of the boats being identical. Even when two boats are made in the same molds, they may not be identical. Variation in lay-up of the laminate may produce variations in the hull weight and hull strength. One boat may have been sitting on a trailer for 20-years with improper support, and the hull shape may have been distorted. One boat may have been in the water for 20-years and picked up hundreds of pounds of added weight from absorbed water. Variations like this will cause variations to the boat speed.