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not very flattering report from Mercury Marine re E-15 use

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I did not get time to review the whole PDF in the depth I would like to (job hunting taking a lot of time ;) ) but a few quick observations;


1) the purpose of the study was likely to see what the average mechanically clueless consumer would experience with his old carb'ed motor since he would not likely adjust the carb's A/F ratios. Not a problem with the fuel but instead shows the difficulty of change for the typical consumer.

2) test also shows serious flaw of using an open loop WOT phase rather than O2 sensor control- especially with marine engines. Marine engines indeed are likely to spend far longer at WOT than autos-- picture boating on Lake Winnebago which is about 40 miles long-- weather coming in and you are 20 miles out!!!!!

3) shame shame shame on these companies for elastomer selection --this is the one thing they could have easily avoided for problems!

4) they do tend to run more hp per displacement than in autos- this means heat, wear, risk of destruction.


These engineers are NOT dumb- I know one of them who is from my town and who was part of an E85 race engine design team in their performance division. It is just that from a cost control view- they cannot go too far beyond their competitors or they will not be competitive.

So what do they do about open loop in EFI?

What about closing/sealing the fuel systems like cars do?

When do they go EFI on the smallest engine models?

How do they implement these changes in the current economic marketplace? (just one year ago they about closed the whole Fond du Lac operation in favor of moving it to Oklahoma- but then dropped the idea)

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I haven't had any trouble with 100:1 synthetics and E10 or even a little higher E percentage.


The heat here is probably my friend though.  Water cooled marine engines run at a little cooler temp than air cooled  so that's not a really equal test condition.

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Having tuned 1/4 mile race boats and 1/4 mile cars there is one other consideration like Phil mentioned.


A boat carries a much higher load once you've gotten to cruising speed compared to a car on asphalt or even dirt, maybe an exception for sprint cars as the turns really load the drive train.


Also missing is the number of times this test has reached it's end per 100 runs vs how many mechanical failures.


One of the more severe tests is running a V8 car engine for 25 hours at wide open throttle.  100 hours to me is really severe.


I feel like it would give a clearer answer of maybe 25 repeated 5 hour tests and then tear down the engine and compare wear, contamination and fuel system viability.

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After a quick browse, I'd tend to mirror outlaw's sentiments.  It seems they just wanted to see what would happen when changing fuels and flogging the crap out of the engines until something blew.


A few quick notes of mine -


I am curious how/if any routine maintenance was performed on these engines.  ie around the Figure 32/33 area they talk about checking valve lash during routine maintenance.  But did they actually adjust it back into spec?  If they just let it run, then obviously there is going to be damage.  Without the valve sealing tight to the head, there isn't as much thermal transfer and the valve heats up, leading to all the problems they observed. I wonder if all the exhaust valve damage could have been avoided due to simple routine maintenance / lash adjustment?


In Figures 41/42 then show two pistons and claim the E15 piston shows carbon deposits from running hotter.  Obviously I'm doing armchair failure analysis here, but it sure looks to me like the rings didn't seal.  To support the 'running hotter' theory, you'd have to believe that the carbon from the combustion chamber above the first ring, just happens to perfectly match the oil carboning below it, and that oil carbon was actually heavier above the oil control ring - where there should be less oil and lighter below it where there are huge amounts of oil.  If you believe the rings didn't seal, then you'd expect the carbon to be fairly even and uniform through the ring area and tapering off toward the skirt - which is about what you see. 


The big key would be looking at the under side of the piston.  If the oil is thermal carboning, then there should be no preference as to whether its on the inside or outside of the skirt. Combustion gas blow-by would tend to coat the outside of the skirt and not the inside.  If you squint and look at the bottom of the piston in Figure 42, it seems the inside is rather clean and the outside carboned which would also suggest poor ring sealing.


I concur it doesn't look like the fuel pump held up very well...no mention of mechanical issues, but a bit of visual deterioration.  This could easily be fixed by selecting more compatible components during manufacturing. 


Lastly, I suppose they would have observed very similar issues with E10 - and why any manufacturer wouldn't be building an E10 compatible engine today is a bit beyond me.

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