I have a 1998 merc 4.3L v6 and alpha I drive. I noticed the rpm's were surging some. I checked the #5 and #6 spark plugs and the #6 was wet. I pulled the exhaust manifold and its completely shot. The oil on the dipstick looks lighter than normal (maybe just slightly milky). I ordered new manifolds/risers and will be changing the oil. Anything else I should do or check before running this engine again. The boat has been run in fresh water lately. Thanks.
