I built an alternator bracket because I was not confident with the current mechanism. The aft end of the engine is covered with an aluminum gear case with the alternator mounted to an ear on the stbd side.
I was skeptical about the strength of that aluminum housing and whether or not it could fail. The Universal M18, M25, and M25XP had failures of their alternator bracket, causing the gear case to fail. I have not run across this failure in 5444/M50 engines and the gear case design is a little different.
Another reason for my bracket is that adjusting belt tension was a pain in the ass. There is the curved arm that has to be loosened and the alternator is fastened to the engine with two bolts that have to be loosened. It was really awful.
Since the engine was out and I needed more welding practice, I made a new bracket that bolts to four of the exhaust manifold studs and three of the gear case bolts. It's adjustable fore and aft to get perfect alignment with the pulleys. The ears for the alternator fit the Yanmar feet (3.15") and it will also work with a single-foot alternator.
The new position of the alternator can use belts between 47 1/2" up to about 50 1/4". I got a 47 1/2" belt.
For the belt tension adjustments I used a threaded connecting rod (12" aluminum) and two rod ends (5/16" stud and bolt hole, stainless). These are fastend to a bracket that is bolted to the oil pan (already had tapped holes for a fwd motor mount if it were in a tractor) and the upper bracket bolted to the alternator adjustment ear. All I do to adjust is loosen locking nuts on the rod ends, and turn the tie rod, retighten the lock nuts: Done.
So far, only drawback is that the tie rods have only about 1 1/4" of travel and that is not enough to loosen for belt installation. I have to remove the tie rod from the alternator, lower the alt, then refasten the rod end and tighten up. For belts that are longer, I have a steel extension that fastens to the alternator so the tie rod can reach.
Verne, I wouldn't worry about that alternator falling off; never heard of it for our 5444 engines. I did this for fun! Engine was out, so I figured I'd make maintenance as easy as possible. I also added a hydraulic hose to the oil pan so I can easily pump out the oil, and refill by reversing the pump.
Do a google search for "alternator bracket failure universal" and you'll be able to see the M25 engine bracket, then compare too ours, which appears much stronger. It still would be one thing to add to your periodic check list: cracks on the gear case near the alt bracket.
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