Last winter when I replaced my exhaust manifolds, elbows and risers, I noticed severe corrosion in some of the exhaust ports, but at that time did not want to get into removing/replacing heads. Of course this issue bugged me all season and I decided this winter to replace the heads. Today I removed the heads from the port engine and took a few pictures for all to see. I am pretty sure the heads are toast, corrosion is so bad in a couple of ports that chunks of metal flaked off. I wonder if anyone has a recommendation for a supplier for rebuilt/remanufactured heads? My engines are 7.4 MPI L29 Gen VI. They are 20 years old. I have owned the boat for about 18 months. It appears moisture sits in the exhaust manifolds after the engines are turned off. In fact when removing my only one year old manifolds there were tiny pools of water sitting in each manifold exhaust port. I had found the same when I removed the old ones last winter. I assume a poor design that unfortunately over many years leads to this corrosion. The water must be condensate, I think? With all new manifolds, risers, elbows and Mercruiser gaskets I don't see where else it would come from.