Re: sparkplugs on a merc 500.
Depends on whether you have the standard ign model or the "SS" model. The magneto-ignition model would take conventional plugs, while the electronic-ignition "SS" model takes surface gaps. However, L78V is too hot of a heat range for a 50HP and instead you should be using L76V's or equivalent.<br /><br />BTW you can use conventional plugs in a CDI model, but don't use surface-gap plugs with magneto ign as the mag doesn't develop enough voltage to fire them properly.<br /><br />You can tell if yours is a magneto if it's stand-alone with no other coil or electronic components connected. The electronic ign model will have a separately-mounted ign coil, and a switchbox (power pack or CDI unit) mounted on the front cowling support.<br /><br />BTW you'll probably get more response posting your Q's over in the Mercury forum!<br /><br />HTH...........ed
