Re: 120hp or 140hp
Just some things to consider about the situation-
I doubt anyone's going to look at the plate but if you've still got 140 on the cowling you could get a ticket for having a "140" on it and then you'd have to fight it because the coast guard/fish and wildlife/sheriff/whoever is writing the ticket may not want to participate in a forensic investigation of the plug to determine a match between the coast guard plate and the block. Your insurance, if you've got it, won't cover you for any accident, at fault or not, that could be related to speed if the motor exceeds the coast guard plaque. Obviously you'd just have to fight them and you'd win because it is in fact a 120, but these are hassles you might prefer to avoid if the option to re-badge it ever came up.