What would cause this

[michaelaraujo]

Thank you all. Have been able to find many answers to questions on this forum. So I Finally got around to taking my starboard 720 apart. Once i got the piston wrist pins out using a pulley I found this. What would cause this? Since I'm going to rebuild would like to resolve any/all issues. Once pistons were removed crank spun fully and smooth.

 

[mikidymac]

Only thing that could is water in the engine. Your crankshaft is shot and needs to be replaced.

 

[michaelaraujo]

Only thing that could is water in the engine. Your crankshaft is shot and needs to be replaced.

While I had cylinders and pistons on I was not able to turn crank a full rev. After removing cylinders and pistons crank spins freely. I haven't been able to get mag and PTO off to get to crank and inspect. For sure my crankshaft is done?

 

[mikidymac]

Yes, the only way to rust those bearings is with water in the engine that would have gotten into the crank also. And the rust in your picture damaged the rod surface which also requires replacing the crank.