Mag 350 Spark plugs

[Paul Williams]

Good evening I'm new to the forum, I want to change the plugs and leads on my Mag 350. I have around 4" between the exhaust manifold and the engine bay. The whole area is really crowded and I can't even see the plugs. Is it worth removing the exhaust manifold or is this too extreme. I am a novice at marine engines but am reasonably handy and have changed plugs on numerous cars. I didn't want to start taking things apart and regret it. Also no idea what the gap should be as lots of conflicting information and I don't have a manual.

Also does this engine have a closed water circuit or purely sea water?

Many thanks in advance

 

[Fun Times]

We’ll need your engine serial number to try and help better also the year of engine or/and boat.

Often there should be a small specification guide found on top of the engine cover or one of the stickers ‘sort of near where it says 350 mag… that sticker if legible would offer the spark plug gap.

 

[Mark S.]

Typically when dealing with I/Os it is not uncommon to have to take the boat apart to gain access. Is it not possible to remove bulk heads/panels next to the engine to gain access?

 

[pismo10]

You can get to them with an open end wrench and some gymnastics. Plugs last along time, contrary to what the sales guys tell you, you can go hundreds of hours on them without issue. Pull the easiest one and see how clean they are.

 

[Alterry]

I don’t know if this thread is closed, but I have the same question and same engine. 2007 Sea Ray Sundeck is the boat, no access to the starboard side.

Interestingly enough when I ask the question is it necessary to remove the risers when changing plugs on a 350 mag, I get two different AI answers on different phones. I just wonder what the human experience is, and if the plugs have a long service life, does it make sense to do everything, ( riser gaskets, exhaust shutters, etc) when you change the plugs.