1977 evinrude 85 problems

[Sherma k]

Hi, looking for answers
I bought a fishing boat with a evinrude 85 1977. It hadnt been in the water since 2003. I rebuilt the fuel system from the tank to the carbs and Replace the water pump. The daughters and i took it out this last weekend for about 30 minute to a hour and it ran good. I took it out about a hour later and after about 20 minutes it started to kind pulse a little then it finally died but started back up but kept acting like it was running out of gas and finnally died and wouldnt even crank over. We got a tow back to the dock where it started back up and we trailered it. I took it out again today and it ran good for about half amile and started doing it again. Any ideas whats going on. I check the primer bulb and it was still full and hard

 

[KJM]

Does the tank have ventilation so that it don't build up a vacuum as the gas goes down? If not sure you could loosen the filler cap when the problem starts and see if this helps.

 

[Sherma k]

Does the tank have ventilation so that it don't build up a vacuum as the gas goes down? If not sure you could loosen the filler cap when the problem starts and see if this helps.

I was wondering if that be the cause but if it is vapor locking wouldnt it collapse the primer bulb. I have noticed the vent hose being some what pinched