I replaced my 4108 with a Beta 50. One big consideration was that I could use the existing 2" exhaust system (Yanmar wants 3"). The 4108 only has about 35 usable hp, and Beta recommended the 37hp as a replacement, but I felt the 4108 was a bit underpowered for my 45' boat.
Two years and 600 hrs on the engine later, I am very happy with the new Beta--its smoother, quieter, and DOES NOT LEAK OIL! When I had a problem with the oil change pump, they fedexed a replacement down to Trinidad in 2 days at no cost.