I bought a boat (not Mastercraft) about 12 years ago. After 2 years of very casual use (total of about 4 weeks a year) the engine failed. The mechanic that replaced it said the block had Jb Weld on it covering a crack.
So I agree with Cloaked, fix it right the first time. The JB Weld might hold up for a little while (or it might not).