Spark Plug Questions

[FYN409]

Spark Plug replacement time, sorry for all of the questions. Anyone have a recommendation for spark plugs for an 88 7.4l Mercrusier 330HP? I am due to change them out, I have not taken a look to see what is in there currently. Does anyone know what the OEM plug was?

Any recommendations on brand? From what I can see in their catalogs NGK lists a BR6FS and Champion a RV15YC4 does that sound correct? Has anyone run the NGK Irridium plugs in their boat? Is it worth it?

Thanks,
Ryan

 

[Quint4]

I am running the NGKs. Read this thread:

http://clubsearay.com/forum/showthread.php?t=33043

 

[millz90]

NGK's

 

[flarepoman]

I put Bosch Platinum Plus plugs in both engines. I also have the 330's That with timming the engines made a world of difference

 

[rondds]

OEM was AC MR43T - it might say that on the plastic cover of your flame arrestor. That's what I'm running now. For several years I used Autolite 25's. When I bought the boat she had Champion RV15YC4. With the limited "mileage" we put on these boats in the NE (and you do in Michigan), I can't see the need for "long life" plugs.

 

[fc3]

MR43T is a good choice for that engine. Good life, fires well, cheap and the M is for marine so it won't rust into the head after a season or two.

 

[FYN409]

Thanks for the info guys, I appreciate it. I am leaning toward the MR43T, with NGK my second choice. If I would go NGK is that a "marine" plug? Would I have to worry about it rusting into the head as Frank mentioned?

-Ryan

 

[Quint4]

NGK BR6FS is marine.

 

[rondds]

I don't think you'll see too many non-marine plugs rust in the heads. The autolites gave me three seasons of service and came out without incident. I put a smear of never-seeze on the threads - and I mean a tiny smear - not near enough to get blobbed into the cylinders. If your hatches are normally protected by the canvas and you don't leave the plugs in for 4 seasons with leaky manifolds, you should have no problem with any plug.