1970 75 (7.5) merc proper spark plug ?

[roonie]

I am looking for the proper spark plug for this engine. My local 2 local marine shops say something different than what is said on a chart i found on this site. My serial # is 2957779 and i have thunderbolt ing. Can someone tell me which is the correct plug. thanks

 

[Fun Times]

Sorry but I'm not completely sure as they seem to offer two sets of ignition systems under your parts guide. Hopefully one of the other members has been through this already and can offer the correct advice. What plug numbers are they saying to get?.. What is installed on the engine now?

33-58194 SPARK PLUG (AC #V40 - FFK) Parts
NGK BUHW-2 SPARK PLUG
CHAMPION L78V
FLYWHEEL, STATOR AND IGNITION COIL

Or,
(CHAMPION - L7J)
AC M143FF
NGK B6HS
CHAMPION L86C
STATOR PLATE ASSEMBLY

Here's the complete parts guide for you.
2529895 THRU 3274632
http://store.oldmercs.com/category_s/873.htm

The service manual for this engine is P/N 90-68647,
http://www.ebay.com/sch/i.html?_fro...l1313.TR0.TRC0.H0.TRS0&_nkw=90-68647&_sacat=0

Below is just some additional info in case needed about the 7.5,
http://forums.iboats.com/Mercury-Outboards/1970

My manual (for what it is worth) calls my ignition system a Phazemaker point type with an internal capacitor (1970 and 71). The Thunderbolt stator you have linked is the aftermarket replacement for my engine (according to CDI). The part number on my stator is 336-3996. It is my understanding from what I have read on the internet (not always the best source), there were two versions of the Phazemaker used in 1970 and 1971. One having an internal capacitor and one having an external capacitor. My stator has two ground wires. One from the stator to the throttle lever/bracket. The other goes from the stator to the lower housing next to the kill switch. There is green wire that leads from the stator to the positive side of the #1 coil and a salmon wire that runs from stator to the kill switch. Only remaining wires are both brown and run from points to negative side of coils.
Phelon ignition

 

[roonie]

thanks for all the useful information. This engine was purchased as non running. It has 95lbs. compression both cyl. so im pretty confident it will run well as the rest of the engine is like new. Ive gone ahead and purchased the BUH-2 plugs. The engine did not come with spark plugs in the hole. I am just building a stand for the engine then its on to fixing the no spark issue ( pulling the flywheel)