NGK R 5671A-9 plugs
 

Hey guys running these plugs in my 600 Merlin with 1071 blower. Boat runs great!! But if I run on hose at all when changing oil and give her any gas. Next time out on water she will have a fouled plug. I know there is no load on hose and this is doing it. But can I safely go one hotter on the plugs to fix this? To a 8? When it fouls plugs it all ways different holes leak down is great!!
Thank u Skydog

denso uriduim I run IQ24 heat range one hotter than your 9s. had the same problem 557ci sterlings with 10:71s. Will be the last set of plugs you'll buy.

First of what u should know is that on NGK..hotter means higher number so a 10 would be ok !

Thank u very much I will switch. One more thing I called Denso and they told me my plug crosses to a IK? Do I want IK or IQ and why?
THANK U Skydog

Not sure what the difference is between IK and IQ. My plugs have IQ24 on them, they are 14mm .750 reach 5/8 socket with washer seal or (z-gap) and the plug wire tip is screw on type. There racing plugs have no removable tip there also $15.00 a piece. The IK and IQ may have difference in this area, but I'm really not sure. I would think If Denso crossed your plug # to the IK, that is what I would use.

Thank u much buddy