Anyone have a rotor do this before?
 

Here's the new MSD rotor in the 350 in my speed skiff. This was after running it 3 times. The middle time was a good 1-1/2 to 2 hour day on the water. It completey burned and charred the plastic. I'm not sure if it's salt water related or just a defective rotor that was spraying spark. The engine was still running strong too!

HEI or points? What cap, coil, and (if HEI) ignition module are you running?

I stick with Delco stuff for the cap/rotor and ignition module, aftermarket stuff hasn't been reliable for me in marine applications.

Send that to msd, I bet they send you a new one.

MSD will probably replace it.

Hate to say it but their dizzys are quickly getting a rep for being of poor quality. Just as a matter of completeness make sure you check underneath the cap every little while for rust buildup.

I'm wondering if the rotor wasn't screwed down all the way or sitting level. Or if the constant bouncing on the water was making the cap bounce around. I put the old rotor back on and no signs of that so far, but I've only run the boat on the river which is nice and smooth. I plan on getting a cap that screws down to the distirbutor instead of using the stock style spring loaded setup. A car doesn't bounce around like a boat does so I could see that being an issue on a longer run like I did.