serial # 05114402,model# E225DHLSOC 2005 etec 225-new dressed powerhead in 2006. had 3 year maintenance done(fuel filter,water pump, lower unit gear lube,spark plugs,engine check) noticed spark plugs were QC10PEPA but spark plug chart says QC10WEP-iridium plugs and engine changed to XD 50 mix-is this correct spark plug and why change to XD 50 setting - it has been on XD 100 setting since the beginning.