[rs127]

polaris sl780 checked pistons and found one that had pockmarks around the outer sides of the top. could this be from water. I would think that preignition would be more in the center of the piston i do not know

 

[NOVA23ZZ502]

Preignition will be all over. I know I melted down a ZZ502 650hp in my 23ft Nova Wellcraft. She now 30 over and turns about 680hp with some extra machine work.