1970 4hp runs 45min dies unless choked

[danny9696]

Hi all I have a 1970 4hp Johnson that runs great and I mean geat for about 30 to 45 min then it dies, I can play with the choke and keep it running good but not great, I figured it to be a fuel problem because the choke keeps it running, I rebuilt the carb, replaced the plugs, the fuel pump seems to be good. I have tried squeezing the primer ball to make sure it was not the pump but it does not seem to matter, anyone have any ideas I am at a loss and I want to go fishing bad!

Thank you all again

Danny

 

[Rick.]

Re: 1970 4hp runs 45min dies unless choked

I have a 71 that would quit after 10 to 15 minutes and did a carb. kit and that solved the problem. If playing with the choke keeps it going, it is fuel/air related. But I'm puzzled that it would run for so long before acting up. I'm all for redoing the carb and at the same time replacing the fuel lines with alcohol resistant lines. Are you certain the tank is venting properly? That could also be your problem. Are you running at trolling speed for the 45 minutes? If at WOT does it fail sooner? Best of luck and let us know how it goes. Rick.

 

[danny9696]

Re: 1970 4hp runs 45min dies unless choked

I ran this engin with the cap off the gas tank when it died, I am going to check the points although I dont think that is the cause. it is a fuel delivery issue I still need to check the fuel pump, but the fuel line is ok, I ran my merc 90hp with the same tank and fuel line and have had no issues, the fuel line is 4' long and maybe its to long to pull fuel through but I kept the primer bulb pumped up, the choke had me thinking it was in the carb so I think I will take it apart again and give it a close look.

Any advice would be great please

Danny

 

[sv fisherman]

Re: 1970 4hp runs 45min dies unless choked

When you say rebuilt the carb, do you mean replaced parts or soaked and cleaned it good?

 

[danny9696]

Re: 1970 4hp runs 45min dies unless choked

I used carb clean and air and replaced parts

 

[kenmyfam]

Re: 1970 4hp runs 45min dies unless choked

Check for air leaks in the lines. How was it before the carb rebuild ??

 

[tashasdaddy]

Re: 1970 4hp runs 45min dies unless choked

vent open on fuel tank?

 

[danny9696]

Re: 1970 4hp runs 45min dies unless choked

I rebuilt the carb because of the way it died, and I ran it with the cap off the fuel tank, but I will double check the fuel lines for air leaks, but I ran my 90hp merc on the same fuel line and it ran just fine for hours.