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496 intake deposits

Old 04-25-2013, 08:59 AM
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Default 496 intake deposits

After removing my flame arrester to clean it I was surprised when I noticed a heavy deposit of black tar on the throttle body plate. There was also a smaller amount on the inside when I opened the throttle and stuck my hand in. It's a 2004 496 mag HO with 190 hours. I can imagine there's some of that now on the valves and throughout the intake manifold.

Does anyone else use a engine cleaner like the Mercury power tune on this engine? I used to use it on my old carbed 454 now and then but I'm just not sure how the EFI will like it. It's nasty stuff.
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Old 04-25-2013, 11:07 AM
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It is belt dust combined with moisture, oil and whatever else...

Replace the belt, tension it correctly and it will decrease dust. There are a few threads talking about this. you may want to clean your pullies with a wire brush before the new belt goes on. Some 496's have more dust... I think some pullies arent aligned as well as others.

The TB comes off with 3 nuts. It might be a good idea to pull it and clean it. Or, take your time with a rag and some throttle body cleaner. (any cleaner, carb, brake, laquer thinner)
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Old 04-25-2013, 01:17 PM
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That's really interesting. I think you're right. I just replaced the belt last season and I've been having a lot of belt noise since.

I replaced the 3 idler pullys thinking the noise was from there but I discovered it's the new belt. I had crossed referenced it at NAPA so it's not a Mercrusier belt.

Thanks!

Last edited by NightHawk; 04-25-2013 at 01:21 PM.
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Old 04-25-2013, 05:52 PM
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Yeah, that is probably the issue.

Does it have the idler pulley for tension or the adjustable alternator bracket?
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Old 04-25-2013, 06:53 PM
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adjustable alternator

I ordered a Mercursier belt and a K&N filter today. At least the filter will keep the junk out.

Last edited by NightHawk; 04-25-2013 at 06:55 PM.
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Old 04-25-2013, 06:57 PM
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The belt tension is tighter than what you think. Very little deflection. Clean the pullies with a wire brush.
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