hi all, i bought a 19' wellcraft last fall and would like to change the plugs this spring. it has "splitfire"? plugs in it now. how long ago were they popular?? i'm thinking they are pretty old. my clymer manual says "AC R42TS". any recommendations?? i've heard "NGK or BOSCH" just lookin' for opinions. thanks<br />p.s. the engine is a mercury mercruiser 4cy. 170hp. 