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496 H.O Mag Fuel Type

Old 03-04-2021, 09:08 AM
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Default 496 H.O Mag Fuel Type

Hey,

Just wondering what everyone's running for gas in their 496 Mag HO, I like always run 93 in my stuff, but I have seen multiple forums saying that the computers programmed to run 87 because it burns faster, and that 93 burns slower due to the higher octane, so you lose out on HP. 93 is a cleaner burning fuel though, so will that add longevity to the motor?
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Old 03-04-2021, 09:17 AM
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Agree 87 is all you need, don't agree 93 will add longevity. 93 will reduce the weight in your wallet faster
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Old 03-04-2021, 09:52 AM
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Anything at all.
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Old 03-04-2021, 09:55 AM
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There was a dyno a while back that tests stock and modified 496/8.1. (Below) There is only a 1/2 to 1 horsepower difference between 87 and 93. Thats it! Lets be honest, in stock form the 496 is a low compression, iron head truck engine. Its basically designed for 87. Even modified or highly modified, I see no difference in speed or power, matter of fact, I think the soot on the transom is worse with 93. Now, 87 marine is better IMHO than street 87 gas station fuel, but thats another topic.


mercury-marine-496-mag-performance-parts-upgrade-magazine-article.html
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Old 03-04-2021, 10:03 AM
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Originally Posted by Keith Atlanta View Post
There was a dyno a while back that tests stock and modified 496/8.1. (Below) There is only a 1/2 to 1 horsepower difference between 87 and 93. Thats it! Lets be honest, in stock form the 496 is a low compression, iron head truck engine. Its basically designed for 87. Even modified or highly modified, I see no difference in speed or power, matter of fact, I think the soot on the transom is worse with 93. Now, 87 marine is better IMHO than street 87 gas station fuel, but thats another topic.


Attachment 576972
Hey, Yeah thats what I usually fill up with is street gas. I trailer my boat between a bunch of lakes and the ocean, plus the gas on land is far cheaper than the gas on the water, even for the same octane
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Old 03-04-2021, 10:24 AM
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87 in your 496. Anything higher is pointless. Tons of stock 496 evidence to show this and some evidence of higher octane being problematic such as sooty transoms and loss of performance.

93 doesn't burn cleaner. Higher octane is only a requirement of the manufacturer to prevent detonation in high compression engines.
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Old 03-04-2021, 11:56 AM
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87
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Old 03-04-2021, 01:32 PM
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87! I also love that the 525 EFI likes 87.
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Old 03-04-2021, 01:38 PM
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Originally Posted by thirdchildhood View Post
87! I also love that the 525 EFI likes 87.
Heck, if you are going to go that far, I ran outta gas once and the 496's got us home purely on Keystone Light. LOL
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Old 03-04-2021, 02:06 PM
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87
Anything else is just going to over-soot your transom.

Just make sure you keep it treated with Star-Tron for ethanol reasons.
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