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Merc 7.4 liter Engine - Spark Plugs?

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Old 05-29-2010, 07:10 PM
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Default Merc 7.4 liter Engine - Spark Plugs?

OK, so I've posted before about my engine with low compression in 3 of the cylinders and it running like crap and blah blah blah. But now...I'm just blown away. So, i got my boat ready for the season, and now it's terrible. It keeps stalling. So, I'm looking through the manual for it, and apparently, i have the spark plugs COMPLETELY wrong. They're all in the wrong spot, but i don't see how i could have messed up that bad. SO, i labeled all the wires to where i have them now and started putting them where the book says they should go, and some wires aren't long enough to reach the corresponding plug thingy that they go in. I'm afraid to pull the wires from the spark plug, because then there's no way I'll be able to put them back where i have them. Any suggestions? Pull the wires out and basically start from scratch or is that a waste of time?
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Old 05-29-2010, 07:22 PM
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bring engine to TDC #1 compression stroke.... remove #1 plug to confirm this...

looking straight down at the distributor and it rotates clockwise..

remove cap and see where the rotor position is relative to that terminal on the cap, usually 11 or 12 o clock if your looking towards the front of the engine, looking from the back

nevertheless, whatever terminal the rotor faces is #1, and using 1 8 4 3 6 5 7 2 that is your firing order
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Old 05-29-2010, 07:37 PM
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but would it be worth it to even bother doing this? For the record, I'm 14 years old and I'm posting this for my dad whose stubborn and wont do anything about it. I know i could map out what we have now, but he doesn't want to do it because he thinks it's a "waste of time".
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Old 05-30-2010, 01:31 AM
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If you have stock Merc wires, and they don't fit from the plug to the Dist terminal, then you have them way wrong, as they are all more than long enough to fit to the correct plugs.

DO you have to do it? No, but if they are on in the wrong order then yes you do, or its never going to run right.

DO as BUIZILLA said in the post above and you will get it right.
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Old 06-02-2010, 01:51 AM
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Is your dist cap labled with the cylinder #s ????
If so its easy and even a 14 year old can do it. Take every plug wire off and start with the longest ones and connect the correct wire to the correct spark plug and correct cylinder position on teh dist cap.
If the cap is not labeled, then you will have to use Buizilla's method.
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