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Recommended octane for 496MagHo

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Old 06-08-2007, 05:55 PM
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Default Recommended octane for 496MagHo

I always use Premium in everything I own, but I've been told that Mercury actually recommends Regular (87) for the 496. Is there any merit to this rumor? I'm looking at a boat with a 496MagHO and if I can save the extra dough and still make it run right.....
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Old 06-08-2007, 07:12 PM
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There may be more information on this subject in other threads. Try the search feature.
I use 93 if the boat is going to sit for weeks. Otherwise I mix 87 and 89. Depending on the availability.
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Old 06-08-2007, 07:16 PM
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87 is the recomendation on 496ho.Anything more is wasting money.
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Old 06-08-2007, 07:22 PM
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I was always told there wasn't much to gain in a low compression engine and to save my money. I always ran 89 in my 415s and never had a fuel-related problem.

There was some time ago that the electronic spark advance relied on the knock sensor to tell it to stop advancing the timing. If you had 93 the engine sometimes didn't EVER knock and the timing was advanced too much. I'm sure after MerCruiser warrantied a few engines they changed that situation in the computer.

I don't know how true that is, I never remember to ask the right people.
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Old 06-08-2007, 07:22 PM
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Not sure if it is relevant or not but same thing with the 502 Mpi' as well. Owners manual even says to only use 87
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Old 06-09-2007, 01:57 PM
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Good, clean, waterless, non-junk filled 87 octane is all thats needed. But remember all bad fuels are bad fuels so if you expierence a lot of knock events on your 496 or other fuel related problems find a new fueling station!

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Ray @ Raylar
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Old 06-09-2007, 02:41 PM
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Only 87.
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Old 06-09-2007, 02:45 PM
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87
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Old 06-09-2007, 04:08 PM
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I own I gas station, so I know what's going in the tank is good stuff.
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Old 06-09-2007, 07:17 PM
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You get the most HP on 87. Buy 93 and you spend more to produce less HP.
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