mercury 25 only runs while pumping ball

[octaneforce]

i have an early to late 80's mercury 25 horse outboard that will only run while im pumping the ball. i replaced the gas tank, fuel lines, fittings, bypassed all the filters, and replaced the ball. the problem has not changed at all. the only thing i can think of is that it needs a fuel pump but i cant seem to find one at my local parts places. the only number i can find on the motor is the serial; 6275143. it seems that nobody can tell me what year this motor is with just this number. i am at a loss with trying to fix this thing

 

[udoittwo]

I am totally new to boat motors and have no accumulated knowledge like most in this forum but, I have a poor copy of a Mercury shop manual. Unfortunately, it doesn't cover anything below 40 HP. IF Mercury uses some sort of standard numbering on their serial #s, I would guess it is a 1983. In 1983 the 50,70, and 80 HP motors begin with 623**** through 627****. Most of the 1982 begin with 597**** and the 1984s begin with 642****.. So my best guess is that your ser. #627**** is possibly a late 1982 but probably a 1983? As best I can tell of the larger Mercury motors of 1982-83, there seems to be little change, so, IF it is either year, it might use the same parts.
Hope that helps so how,