Help with 1969 vintage sterndrive

[mynorac]

I bought an old (1969) boat a few years ago and have had it in the water a few times. When I went to get the boat I noticed that the lower part of the sterndrive had a crack in the forward part of the gear housing. This is a very old boat that I got for little money and I don’t want to invest much into it. I know very little about boats but I’m pretty good at do-it-yourself projects. This 1969 Sabre Craft is equipped with a 120hp 4 cylinder engine. The upper portion of the sterndrive is labeled Mercruiser 120/140hp and the serial number may be 2791168 but is very hard to read. I really could use some help identifying this model sterndrive if I have to purchase parts. See pics. I did remove the lower drive assembly and inside it has the number 1623-5412. When I removed the lower drain plug a bunch of water came out with the oil. I think this may have caused the crack. My question is, can this unit be repaired? One thought is to try to pump cleaning solutions into the drain hole then using something like JB weld. After reassembly running and flushing the lower unit with good oil several time before a trip to the lake. My other thought is to completely disassemble the lower unit and weld the crack. The second choice is the best but it looks like I might need special tools. Any other ideas?