Suzuki DF 250 two blocks cracked in the same place

[cali kid]

Customer purchased a used, low hour '07 DF 250 Suzuki from me to replace his port side counter rotating motor of the same specs that had failed with a large crack in the outside of the block behind the starter. The failed motor had approx. 600 hours on it. I have never seen that type of failure on any motor before. I install my perfect running used motor on his boat, test run it, does great, customer uses it for a month, low and behold, it cracks in the exact same place. The boat is a 28' Triton CC. I am obligated to replace the motor on my dime, but I know the replacement will fail the same way for the third time. Oddly right before the first engine failure, new four bladed props were installed. The boat ran for 12 years trouble free with 3 blade props. Could the props be causing this disaster? Some odd vibration going through the motor? Just on the port side. Anybody here ever seen, or heard of anything like this before? Any thoughts or opinions are greatly appreciated.

[cali kid]

I will post pictures of the cracks as soon as I can.

[cali kid]

[cali kid]

The crack goes from the voltage regulator to the thermostat housing. The motor still runs on all 6 but is getting water in the oil.

[FMP]

Vibration stress or overheating or both?
Turned too hard to starboard over rev ?
Slightly misfit tolerance ?
Crank walking?
Weird

Check all the mounts

[Whaaaaat]

Don't those have a driveshaft bearing in the midsection? Could the driveshaft be trying to push the crank out the top of the block?

[Motv18]

That almost look like lugging or knock damage. Might pull the rod bearings. They could be doing some weird one engine operating.

It it looks like some block cracks I’ve seen where the heads blew off racing.