I have a 1977 70 HP Evinrude (70773S). I was getting ready to install a tell tale to monitor water pump function. I pulled the head to look into the water jacket for the best place on top for a fitting and got rather bummed, The top and middle cylinder had a light rust film. The bottom cylinder looked normal. The engine was not stuck and I could turn it by hand with the flywheel. The rust was easily removed with a shop cloth and oil and left no pitting. There is no scoring in any of the three cylinders. I am concerned that the rings may be affected too. The engine was last run in early December and spent the rest of the winter on the trailer in the garage. The head gasket does not appear to be leaking. Because I can't see any cracks in the head or affected cylinders I suspect that it may be a problem in the exhaust manifold. While inspecting the head I noticed that the cylinder head combustion chambers are clean as in steam cleaned, The piston tops were carboned up however. I don't think problem this is a flash rust issue from not fogging. The exhaust ports in the top two cylinders seem moist. This motor usually runs in the Patuxent River which is a tributary of the Chesapeake Bay. It is salt water but the salinity levels are low. It always gets the muff flush at the end of each run. I went to the search section and did not see much about exhaust manifold and this problem. Did not mean to ramble but I tried to provide enough information to go on. The last time I did a compression test was two years ago and it was an even 125 psi in all three cylinders. The motor has always performed well and never overheated. The water pump is two years old.
Thanks
Tony
Thanks
Tony