Siezed engine - water in cylinders and pan

[MikeDSmith]

I just bought a Coronado 34 with a seized A4. The old owner said it ran fine until after he changed the plugs. After the plug change, it froze up and never started again. I pulled the motor out of the boat. Pulled the head. There was water in the two center cylinders. Some rust in the outside ones as well. I filled the cylinders with Marvel Mystery oil for a day, but that didn't help. I dropped the pan and disconnected the rods. I ended up having to beat the pistons out with a rubber mallet and a piece of wood. There is rust on the pistons and cylinders. The engine sat for about a month locked up before I pulled it. The head was pretty tough to get off and I mangled the gasket so much that I can't really tell if it was messed up already or not. There was quite a bit of water in the oil pan as well. At this point, I'm trying to figure out if it's worth rebuilding. Do you have a list of steps for figuring out how the water got in? How do I go about narrowing down the possibilities. Thanks

[JimG]

Changing the plugs indicates "wouldn't start" which leads to the conclusion that the PO cranked the engine for a long time with the raw water port open, which flooded the engine through the exhaust system. Sounds like it's salvageable.

[bayway27]

Would one ream the cyclinder walls to clean out the rust or bore to the next acceptable size? Are new pistons required, if not, how is the rust removed and tolerance still maintained if not boring?

[Don Moyer]

Mike,

Given the passage of time since the water got into the oil pan, it may be very difficult to tell for sure how it got in. The attached guide may give you a few ideas.

Don

[Don Moyer]

I can't recall your earlier postings, but many people have cleaned mild rust from cylinder bores using crumpled up newspaper. If the engine is disassembled so that it can be cleaned properly, 150 to 200 grit sandpaper will work, and it is seldom necessary to re-bore just as a result of rust. You should measure your bore to make that determination. If you have a copy of our service and overhaul manual, you can find this guidance on page P4-3.

Cylinder bore wear: The greatest wear will occur 1 to 2 inches down from the top of the bore and be slightly elongated from side to side. I feel quite safe in leaving the bore "standard" so long as the highest reading on any bore does not exceed 2.565" (.002" over the maximum published value of 2.563").

Measurements of 2.566" (.003" over standard) would involve a discussion with the customer regarding future plans (heading down the intracoastal waterway etc.), and whether or not the engine had been experiencing blowby, poor compression, etc.

Engines with bore measurements of .004" or more over the standard range are usually better off being re-bored to .010" over standard."


Don