I went and opened this can of worms before we had spoken. Pretty confident the cabin plan we discussed will be copacetic.
Printable View
Ok, now im going to disagree with you ;) If the hole is 6.0 and the center to center speaker bolt hole dia is 6.3, that leaves no deck for the screws to bite. In other words, the center of the speaker holes with be .15" away from the cutout. The diameter of a #8 screw is .164. The screw will break through into the existing 6" cutout.
Well, I glad they have stayed put, but how many hours have you put on the boat this spring since you installed them? A few good choppy days I see the screws breaking out to the cutout as worst, or hair line cracks in a season ro two at a least. I would suggest a backing plate for you as well. This is not about a particular brand. This is about 90% of the 6.5" speakers on the market. They are all very close in their physical specs.
Don't Jinx it HAHA
I had different speakers in the same hole for 1+ year. No issue. (I'm going to measure it properly over the weekend, if it's exactly 6" or less than that)
http://i643.photobucket.com/albums/u...psf30b873c.jpg