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Simplest Spark Plug Question Beating my brain

L

lenny

New member
"I was just given a 1974 Runab

"I was just given a 1974 Runabout with a 140 OMC I/O motor Model No. 990225A. This is my first boat. I want to change the spark plugs and there were 4 different types in the existing motor. Ac delco (MR43T), champion (RV8C), autolite (Smudged) and a NGK (DR5HS). based on the information I have found, it lists the NGK B6ES, this plug is larger than the ones that were in there. Any help would be greatly appreciated. Thank you."
 
"Go with the AC MR43T Delco. T

"Go with the AC MR43T Delco. They are standard on just about all Marine engines it seems. Any autoparts store can cross reference the plugs for you if you ask. AC MR43T is same as NGKBR6FS, which is the same as Champion RBL8 (new number RV8C), AC Rapid Fire #10. The MR43T is the Marine version of the R43T car spark plug. One stainless, one isn't. MR= Marine. Looks like you had two right plugs, the champion and the delco."
 
"Actually, M is for marine, R

"Actually, M is for marine, R is for resistor. You can call Mercruiser, tell them the motor serial number and they can tell you what is supposed to be used. MR43T is a safe bet, though."
 
Thank you all for the great fe

Thank you all for the great feedback. I appreciate it. I ended up going with a NGK 6630.
 
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