I have a 305 engine with a cracked block. The engine seems to run fine yet. Is it possible to weld?

Question

The engine is in a 87 bayliner with an OMC cobra drive. It is a 230 horse motor. What are my options??

Answer 1

No one in their right mind will attempt to weld unless it is out, and dis-assembled. You have to control the applied heat to acheive good results. If you go to all the trouble to pull it, I would just get another block.

Dpending on the crack location, you can fix it without welding via the epoxy route. This isn't a permanent fix, but may last several years. You have to "stop drill" the crack at each end (you do this to weld as well), then grind off the outer surface, "vee" the crack, and apply the epoxy. JB Weld works well, as others.

Yours is probably cracked around the bottom of the cooling passage, below the freeze plugs. Drill and tap in 1/8" setscrews at each end and try the epoxy. If a small leak remains, you should be okay if your bilge pump works. I mean you are not gonna drain your radiator are you?

If you can physically get at the crack while the engine is still installed (may need to pull the exhaust) try the epoxy. It will be cheaper and less trouble than welding.

Answer 2

It depends where it is cracked. There are parts of the block that are not structural, but the crack will sometimes travel to something critical. If it is a water jacket and leaking externally then there are a few ceramic type engine sealers that will seal the leak but will not fix a crack. If it is cracked across the deck (the head gasket surface), then it is a more complicated fix that will involve cutting away the cracked area so that a weld can penetrate and then have the block remachined (better to look for another motor) . My advice? keep a close eye on the water temp and the oil pressure and condition (watch for a goopy mix that looks like chocolate milk) and run it as normal. I worked at a junkyard years ago and it was amazing how many good running engines had cracked blocks (some right across the lifter valley) upon inspection. I agree with Mr Dirt, welding cast iron it is a skill that few welders possess despite their assertions.

Answer 3

If it is not in the combustion area, it could be welded or brazed.

The problem is that who ever repair welds it had better know what they are doing. It takes a lot of skill, and knowledge to repair a cracked block. A lot of welders can throw welding material over the crack, but you need someone who can repair it. Not the same thing.

So the question is not if it can be done, but can you find some one who can.

If you can't then it would seem to be that replacing the motor is better then being adrift and at the mercy of the currents.