witch spark plug's for 3.0LX 1993

Hi, Just returned home with a set of plug that i'm worried about being too long. Their AC MR43LTS, but my manual calls for #MR42LTS... Current plugs that was in engine was NKG BR6FS and the threaded area is about 10mm vs the 15mm on the new AC plugs. Worried about that one number3 instead of 2 on the plug number's... Also worried that if there too long they might hit piston..Engine serial number is 0F067528, and it's supposed to be a 1993 3.0LX...Also woundered if the plugs that were in engine were wrong, could this have caused some of my rough idle problem's...Thanks all!

Re: witch spark plug's for 3.0LX 1993

Not sure what manual you are looking at, but Mercruiser calls for the MR43LTS in both the service manual and all their parts lookup programs.

Did it cause your rough idle? I doubt it, probably needs a carb idle mixture adjustment.

Re: witch spark plug's for 3.0LX 1993

Lots of things can cause a rough idle in a 20 year old motor. Have you checked the compression? When was the last FULL tuneup?
Carb adjustment as I mentioned before. Do you have a water separating fuel filter installed? If not, it would be a good idea to do so.

Re: witch spark plug's for 3.0LX 1993

Don S said:

Lots of things can cause a rough idle in a 20 year old motor. Have you checked the compression? When was the last FULL tuneup?
Carb adjustment as I mentioned before. Do you have a water separating fuel filter installed? If not, it would be a good idea to do so.

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Thanks again Don,No water separating filter yet, but did clean tank out and put in fresh fuel.Info for plug number came from Seloc manual volume2 for 1992-1996 mercruiser sterndrive...PageA6 near back of book that had a note(3) concerning plug for 3.0LX...This concerned engines with DDIS ignition using AC#MR42LTS plug's, but offered no info for EST ignitions.. I was worried I may have wrong plug's..Just re-built carb and fixing to re-mount it and replace those plug's and wires too.Bought a timing light to check timing (1degree BFTDC) once I shunt those two wire's on dist....Will get some help with checking my compression since I did it wrong last time...All cylinder's pumped up to 150 psi then slowly leaked down...You told me to do a leak down test too... Thanks so much.

Re: witch spark plug's for 3.0LX 1993

Info for plug number came from Seloc manual volume2 for 1992-1996 mercruiser sterndrive

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That is why everyone says to use the OEM manual, and not the garbage aftermarket junk. There is so much information copied wrong it's scary. You need OEM manuals 13 and 14 for accurate information.

http://www.4shared.com/office/4afH7vrk/13__GM_4_cyl_90-97.html?

http://www.4shared.com/office/2V0kM3lL/14__Alpha_I_Gen_II__Drives_91-.html?