Mercruiser - Change Spark Plugs

Changing spark plugs in a Mercruiser stern drive engine can be difficult. I am changing the plugs in my 1998 5.0L Mercruiser. The main challenge is that these engines have exhaust manifolds with a water jacket for cooling. The water cooled manifolds limit access to the spark plugs and require special tools and methods to remove and install the spark plugs. Standard spark plug sockets don't fit and even thin wall sockets have trouble. I think that I will encounter this same problem on my 4.5 Liter V6 because the designs are very similar. I do have some techniques and tools that work.

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[williambrown]

Great information never change them out on a cruise always had an outboard. Thanks again.

[mikebruegger]

Maybe give Metrinch a try. They fit wobbly because each one is for metric and standard. They push on the walls instead of the points of the bolt. Give them a They can be angled more from the plug and no biggie.

[Markbarber-op]

For those out there with the new 4.5L V6 the plugs will come out with a standard spark plug socket. If you have the room to get down and dirty the hardest part was getting the boots off, but I was able to do it with my fingers. If you are doing it blind the spark plugs are tilted down and slightly forward. The book has them torqued to 22ft.lbs. Good luck!