I have a 1974 15hp Evinrude that has developed a starting issue.  For the first startup of the day, it takes upwards of 20 mins of pulling to get it going.  Generally I finally get it started with no choke, just pulling constantly until I get it to sputter and finally to turn over.  After I get it going once, it’s back to its normal self and starts on the first pull every time for the rest of the day.  No issues with power or anything, runs very smooth at high or low rpms.  I thought it was a fuel line issue, and replaced my primer bulb to no effect.  Wondering if it’s a choke issue, seems like fuel delivery is the problem until the motor starts sucking on its own.  Any ideas?  Hesitant to rip open a carb or fuel pump if I don’t have to.