Use a piece of glass and emery paper.----Resurface the cylinder head and install with a new gasket.----All 1992 cylinder heads are warped.----You have replaced the water pump impeller ?----Outboards need a new impeller about every 5 years.
Yes they were thirsty.-----The V-4 50 only had 2 big holes for the 2 barrel carburetor.----The 85 HP V-4 in 68 also had a 2 barrel downdraft carburetor.
I have done----Silver solder.---Alumium brazing.---Brazing with bronze.-Aluminum TIG welding.----Stainless welding.----Stick welding of course.-----I do not think welding this engine block is a good idea