Exhaust manifold

[gshldon]

just wondering if there is anyway of checking to see if the exhaust manifold on a mercruiser 898 has any cracks on the inside that will leak water into the engine. There are a couple SMALL cracks on the outside edge of the manifold. I used JB weld on them and that stopped the leakm but i am just wondering if you can tell if there are cracks that will cause engine problems.

Thanks