I have also repaired several 2.5s with marine tex, jb weld, west systems, devcon, waterweld and some starbrite aluminum putty stuff. Myself i like jb weld, west systems and devcon best. Those 3 are kindof used in different applications tho. Prepwork is very important it must be clean oil free and no paint. I have used pounds of jb in the cases of 61x and 62t yamaha ported cases with great success. As long as the prep was properly done ive never had any of it come apart. I have 1 set of cases that has had several cranks put in it and a few spectacular failures and still no issues with the jb. Keep in mind this case i speak of has a 10mm stroker crank in it and a 1200cc DASA billet topend on it. The cases origenally came with a 701 topend on it and hp has surely doubled. If you port the cases without the jb you end up with holes you can stick few of your fingers through the holes. So if it hokds there it will surely work as a case or transfer tunnel filler.