350 MPI Spark Plugs

[Harley558]

I have a 2000 Mercruiser Horizon 5.7. OL 397915

What are the correct spark plugs for this engine? And would you recommend using "Iridium" spark plugs? I don't have the special tool to gap them if the are not properly gapped for my engine.

 

[Zackman]

Re: 350 MPI Spark Plugs

If fresh water cooled then the Mecrusier PN 816336Q cross references to AC MR43LTS or NGK BPR6EFS, both good plugs and more than adequate for this application. All it takes is a set of feeler gauges to check and set the gap.​

 

[TilliamWe]

Re: 350 MPI Spark Plugs

MR43LTS is the plug. And in my opinion, iridium is a big waste of money. And I'll also bet you that when you change out your 9 year old MR43LTS you won't notice a difference. A spark plug gap tool is on the counter at every AutoZone, and costs $.99. Get one.

 

[Utahboatnut]

Re: 350 MPI Spark Plugs

When I put new plugs in mine I thought I would try the iridium's they were alot more money and I didn't notice one bit of difference none.... I'm sure they are a fine plug but not worth the extra money IMO.