OMC 800 Upper gearcase welding

Hello. I'm a new registrant on this forum but have been reading and learning here for some time. My father bought his first boat this spring - 19' Doral with the 3.8L OMC (1982 Stringer drive). The boat has very low hours and despite my concerns with this type of drive it worked very well for us all summer.

We recently pulled the boat out for the winter and it is left to me to winterize/maintain as I am the closest thing to a mechanic in the family. When cleaning and inspecting the outdrive I noticed that part of the upper gearcase casting had cracked and separated - right where the tilt gear quadrant is fastened. Basically, as new boaters we hit something earlier in the summer and we though we got away with it as we could not find any damage while the boat was in the water. However the impact sheared the middle bolt of the three that secure the tilt gear and it broke the corner of the gearcase section that the gear is fastened to (where the lower bolt is). I'd obviously like to get this fixed and from what I've read this can be TIG welded with an aluminum rod. I would like to know though if I have to completely disassemble the entire gearcase first. My thought is that since the area to be welded is away from the seals, etc. that I might be able to get away with leaving everything in place.

Any advice would be appreciated.

Re: OMC 800 Upper gearcase welding

I think you'll be fine. Aluminum dissipates heat very readily so it won't be intense in any one spot (other than the weld puddle). I'd warm it with a torch, weld some, wait, and weld some more. That gives it a chance to cool between.
Remember to clean it meticulously ?" back from the seam area first for a sound weld.

Re: OMC 800 Upper gearcase welding

Aluminum conducts heat EXTREMELY well! Weld one end of a steel bar and you can pick it up a foot or so away from the weld. Do the same weld on an equivelent aluminum bar and you better not touch it within 6 feet of the weld unless you want to loose some skin. I've done a lot of TIG welding and it only took once to figure that out when I started!

I would be concerned welding on your assembled housing assuming it's about the same size as a mercruiser. Not real familiar with the OMC configuration so it might be OK.

Can you post some pics?

Re: OMC 800 Upper gearcase welding

Thanks for the replies. I'm hopefully going to work at my Dad's this weekend so I'll try to take some pictures and post them.