The JB weld or Alumaweld for aluminum are a good option. Dimple the area or rough it up a bit to help it adhear to it. Fill the hole with a piece of metal that will cover as much as posible. Maybe make a little cardboard template from the hole. I have used and had good success with a product called MarineTex.
What I have seen happen twice is the chain will pile up on the bottom of the gearcase guide until it cracks the case in half as the sproket keeps feeding the pile. You wee lucky with just a hole, if you consider that lucky.lol

 

make sure you clean it very good if you are going to weld it i have tigged a few and the oil comes right out of the the material the oil makes a mess when your trieing to weld it

 

hey i have a sport 400 and have had a lot of experience with breaking chains and gear cases. Yes the cases are very expensive. I have found that the hpd chain tensioner seems to work really well for keeping chains on. for the case... if u dont want to buy a new one i would get it welded by a professional. make sure that it is totally disassembled and that when he welds it nothing gets on the inside or where the seals go. Another thing i dont know about your gearcase, but mine is aluminum. so it must be welded with a special aluminum welder. and as for the tear down process i can have one out in 45 minutes and back in, in about an hour. well see if that helps ya.

 

Thanks. Well im pretty handy with the welder myself! [img]i/expressions/face-icon-small-wink.gif[/img] I can tig/mig stainless, alum and steel. I build alot of things for fisherman, like antenna stands, some exhaust work, swordfish stands, herring drums...so i have the gear to do it. Somthing delecate like this would take some time and i have a few friends in metal fabrication that are WAY better then me, so i know they could do it.

But thanks again guys..i'll keep you posted on what happens.