Hi wondering the best way to replace the port side rear (transom end) Cylinder Spark Plug on a 2006 496 Mag HO engine. It looks like the oil filter line/hose connector is right in the way and another hose as well. Looking for advice on how best to replace the spark plug and wire on this cylinder. It's a single engine and I do have some room on each side of the engine to get under the engine hatch and work on it but not much room. Thanks in advance for your replies.

That one is the worst.
Lay on top of the engine, and reach your arms down. That was my best method to get to it.

I also advise using an extension with a wobble on the end of it.


It used to take me 2 hours to do 7 plugs. And another 1+ hour to get that last one done.

Maybe not one of Mother Mercury's best ideas for maintenance.

nor the .060" gap sparkplugs.

Two wobble sockets, 3 beers and laying on your chest across the engine for the entire time. FYI - be sure and check your wire harness across the top during and after to avoid any wires coming loose or slightly pulled while this occurs.

Well hopefully the Merc Engineer that came up with that rear spark plug hose layout/ design is no longer with the company! I sure would like to watch him or her try to swap out that plug in my boat configuration. Well that's 1 big advantage to the future of electric marine power is no spark plugs to deal with!

I had to slightly bend/move the oil line and used a spark plug socket with a swivel joint. I was able to lay a little bit down next to the engine to at least get my eyes on it so it wasn’t that bad. I’d tighten the gap up a bit too on the new plugs.

I used a 1/4 inch extension with a 1/4 ratchet it wasn't too bad also loosen the clamp that holds that oil line

^^^^^ Yes!

I found one of these that has a thinwall 5/8 with the wobble extension on Amazon with the extension permanently attached, then I hooked another wobble extension to it. Between all three ideas you will get it out easily.

To put it back in, I used another thin wall 5/8 on a 6 inch extension with a good rubber washer inside so it didnt move. With a little patience, you can feel the threads catch and screw it in the first 10 turns by hand.