Re: '78 Merc 200 (20hp) Spark plug number?
ShafferNY: What is in there? The same thing happened to me when I picked up a 74 9.8 HP last year - wrong plugs in it. Looking back, it actually ran just fine, but I thought it ran a little better when I replaced the plugs (key word "thought" - not a cut and dried difference). The plugs in it were a gapped plug, the ones called for are surface gap, the same as yours, L78V (actually L77V which has been replaced by L78V).<br /><br />Just as a matter of curiousity, I'd be interested to hear if you actually see an immediate difference in the plugs when you put the L78V's in.
