mercury 75 horsepower 4 stroke model number 1-f75412zd

by piero
(kardinya, western australia)

my mercury motor has been with my mechanic for 12 months and he cannot resolve the problem. he tells me that the 4th cylinder is not firing but other than putting a new carburettor everything he has tried has not worked. he does not want me to buy a new carburettor as he does not want me to spend the money in case the carburettor is not the problem.

I would appreciate and advice you may have so that I can pass it on to my mechanic.
my email address is pguerra2@bigpond.com