merc 4hp wont stay running

[dc363]

i have a 1973 merc model 40 4hp serial # on transom bracket 3535530. i have replaced all fuel lines, replaced all gaskets and check valves in fuel pump. replaced needle valve. carb has been cleaned and has fresh fuel. new primer bulb and fuel line from new tank.the problem im having motor will run fine for a few minutes (5 or so) then stall out.seems as if fuel pump cant keep up. any suggestions would be helpful thank you

 

[hdman97]

Re: merc 4hp wont stay running

Try squeezing the bulb when it starts to die.
If no blockage in fuel line I would say rebuild fuel pump.

 

[dc363]

Re: merc 4hp wont stay running

fuel pump rebuilt. said that in post. any on have other ideas?

 

[hdman97]

Re: merc 4hp wont stay running

Any difference when squeezing the bulb?
The tank have a vent that opens?

 

[dc363]

Re: merc 4hp wont stay running

tank is vented and open. will stay running if i squeeze the bulb before it stops running

 

[neamakri]

Re: merc 4hp wont stay running

check compression if ok, check carb settings, low speed / high speed screws setting per manu. specs.

if you have 2 carbs, you need to synch carbs ( start with settings ) make sure both carbs have same settings.

 

[hdman97]

Re: merc 4hp wont stay running

Sounds like you maybe sucking air, check fuel line and clamps at carb and at connector where fuel line enters engine. Might try spraying something at these locations.
windex,wd40
Carb float could be off also.