All depends on where the crack is, I had a customer who was on a tight budget and had a crack on the exterior of the block, running horizontal for 3 inches with water spraying out when running. I was given a 1 hour max. allowance or he would have to let the boat sit for a couple years before he could afford to replace the engine. I used my die grinder to cutout a "V" notch along/into the crack and filled it with JB Weld epoxy, boat has been running 2 years not without an issue, and no leaks.