Re: mercruiser
The ring gear is easy to change if you have the proper tools.
Remove the drive, then the engine and flywheel.
With a big chisel, knock off the old ring gear from the flywheel.
Take the ring gear to NAPA and match it up with a new one.
Then, heat the new ring gear to about about 400 to 450 degrees and drop it down over the flywheel.
Put the engine back in and realign the engine and put the drive back on.