If I remember old stories, the MH gear had TWO service covers and the M only had one. With that in mind, Why is a M gear behind a 12v71?
Oh, Send more pictures Please. I do like a clean ER.
I had to replace a rear crank seal on my port 12v71ti. Made a wood rail to slide the TD514 back about 8 inches. Dropped the flywheel and was able to service the rear oil seal with just room for my arm to fit in.
I used threaded rod to draw the gear back into place.
If I had to pull that gear, I would consider selling the boat.