I have a 2000 454 mag mpi, which again needs a new starter. I put a new one in 2 years ago.

Wondering if anyone knows of a heavy duty starter, or who has experienced a similar problem.

Thanks in advance!

Just curious, what happened to it? What's it doing?

Lot's of starter issues are corrosion related and can be easily repaired.

Just clicks 2 batteries fully charged. Starter solenoid is fine. Voltage at starter drops when key turned. Engine can be turned by hand.

Very well may be corrosion related, the starteris at the very bottom of the block, and motor is mounted low, a little water in the bilge, and the starter would get wet.

Any advice would be appreciated!

If the voltage drops excessively (below 8 Volts or so) at the starter when you turn the key then the voltage is probably being dropped across a bad or corroded connection prior to the starter. Check all your cables/connections between the battery and starter.

Otherwise you may need to remove the starter and clean it up. All the connections and the case should be cleaned. In some units for example (i.e. my old 1992 454) the case itself must carry the current to the brushes and corrosion on the case edges will cause problems. It's also easy to test the starter once removed and it's unlikely you need to replace a 2 YO starter.