exhaust crack

[ray chellew]

i have a 15hp model fmh5 2004 model it is used in salt water all the time but rinsed with fresh water after use .i discovered yesterday that i have crack in the exhaust chamber where leg mounts onto the cylinder housing this is very unusal as there is no salt water in this area to me looks like corrosion from the inside has taken place, the motor still runs fine with out the cover on but as soon as u cover the motor it chokes obviously as exhaust fumes are sucked into the carb .
is this known problem with this model or what do usuggest.
thks ray

[boats.net]

No we haven't had any corrosion problems on them.