I bought a 2004 boat with a Volvo Penta 4.3 GL with what was described as an overheating at speed problem. All of the basic troubleshooting of water flow had been done by a boat mechanic and the next step was to tear the engine down. The owner had already replaced the engine once due to a winter freeze up in crack in block and was having this problem with the second motor in and decided to pull the plug and sell the boat as is.
I pulled the heads and found rusty cylinders, valves, etc in the number 2 and 4 cylinders. I honed the cylinders and they cleaned up a bit but there was quite a bit of pitting and some lines that I assumed were water lines. I then noticed that the brass freeze plug right between those cylinders was pushed out almost completely. Based on this I assume that what I thought were water corrosion lines may be cracks in the cylinder wall. I was also told they never got the boat to run right with this second engine. This engine had a 4-barrel carburetor while the original was a 2 Barrel. The first engine failed clearly from a freeze up in the winter with a crack in the lifter valley. I was given this original Engine with the boat so I bought a used short block and put the original heads and intake and two barrel carb on it and installed it.
I cleaned and inspected the manifolds and risers and they look okay. There are rust marks inside the ports from the two soon as it had water but it's heavier where the end of the engine and lighter as it goes away kind of like the water was blowing out through them as opposed to leaking from a crack down into the cylinders unfortunately I don't have anyone around to pressure test manifolds and risers.
I guess my question is, has anyone ever actually seen cracks inside a cylinder wall caused by a freeze up? I still can't be sure if they are cracked or just rusty water marks in the water enter the cylinders. Unit through the crack but some other way.
I just need to put on the second Riser and then the engine is ready to start and run but I am Leery and don't want to ruin this engine. Thoughts and recommendations would be greatly appreciated.
I pulled the heads and found rusty cylinders, valves, etc in the number 2 and 4 cylinders. I honed the cylinders and they cleaned up a bit but there was quite a bit of pitting and some lines that I assumed were water lines. I then noticed that the brass freeze plug right between those cylinders was pushed out almost completely. Based on this I assume that what I thought were water corrosion lines may be cracks in the cylinder wall. I was also told they never got the boat to run right with this second engine. This engine had a 4-barrel carburetor while the original was a 2 Barrel. The first engine failed clearly from a freeze up in the winter with a crack in the lifter valley. I was given this original Engine with the boat so I bought a used short block and put the original heads and intake and two barrel carb on it and installed it.
I cleaned and inspected the manifolds and risers and they look okay. There are rust marks inside the ports from the two soon as it had water but it's heavier where the end of the engine and lighter as it goes away kind of like the water was blowing out through them as opposed to leaking from a crack down into the cylinders unfortunately I don't have anyone around to pressure test manifolds and risers.
I guess my question is, has anyone ever actually seen cracks inside a cylinder wall caused by a freeze up? I still can't be sure if they are cracked or just rusty water marks in the water enter the cylinders. Unit through the crack but some other way.
I just need to put on the second Riser and then the engine is ready to start and run but I am Leery and don't want to ruin this engine. Thoughts and recommendations would be greatly appreciated.
