We just bought a 2010 390 Sundancer...

[cbruck]

We just bought a 2010 390 Sundancer with 496 Mag engines.  I was thinking about replacing the spark plugs since I don't know when there were last replaced.  Is it possible without taking anything off the engines?  Are there any "tricks" I should know about before I embark on the journey such as special tools etc.  The standard plugs are the ACDelco, does anyone have experience with the NGK Iridium plugs.  Any and all help is appreciated.

[wai_phung]

I/O or inboards? I'm not sure how your engines are spaced apart in your ER or how much room you have in your ER, but my 07 350 have the twin 496 and its tight where the motors sit side-by-side. I purchased the NGK and they ran fine. I also bought a spark plug boot plug remover, since its can be difficult to remove the boot without possibly tearing the rubber boot. Also had bought from amazon 'GearWrench Tools 41740 3-Piece 5/8-Inch Magnetic Universal Spark Plug Service Kit' which has the different length of extensions for the ratchet. Hope that helps

[340_Sundancer]

I changed mine in our 04 340 with 8.1s inboards. I used AC and it made a big difference. I found one plug cracked on the Stbd engine Stbd side. I have a water hose on the center of my manifolds that obstructs access to one of the center plugs. I suggest removing it to get a straight shot at the center plug. (I think that is how the plug got cracked in the previous owner's plug change.)
Plug wire puller for sure! and some dielectric grease for the wire reinstallation. I used a torque wrench on the installations.
good luck! it is not a difficult job.

[cbruck]

Thanks both of you for the comments, there are very helpful. They are I/O's but I probably have more room side by side. I think the plug wire puller and the spark plug kit will both be good ideas to purchase. Thanks again for the help.

[TimboSlice]

BTW 496 Mag's are notorious for "eating" spark plugs - so replacing them now is a good idea as a benchmark...

[cbruck]

I did replace the AC delco's with the NGK Iridium plugs and seems to run great. The spark plug tool kit is a must. I still had to install the plugs entirely by feel on the outsides of the engines. I might have been able to drop the engine hatch lifts to get better access to the outside plugs. Thanks again for all the help.