1973 Mercury 850 fuel problems

"My '73 Mercury 850 runs g

"My '73 Mercury 850 runs great, except after it has been shut off for a short period of time, like while fishing. The engine will start up fine, but then as I speed up it seems to run out of gas. I can then pump the primer bulb until stiff, and it will start and run fine. I have replaced the fuel line from the tank to the motor, and re-built the fuel pump. I also checked, and cleaned the filters in the carbs. Any suggestions for fixing this problem?"

"Hi there!


Is the fuel ta

"Hi there!


Is the fuel tank vent open?
Is the primer bulb 100% I've known of new ones going dud...
Did you get the re-build of the pump doen correctly?
Is the seals on fuel line connectors seated nicely? Could be sucking in air.
Pick up in tank could be blocked or restricted...


Do this test and get back to me, when out next time, keep the bulb primed and stiff. Do this when on the plane and do it for a while. If the problem is gone, then we can ignore the carbs, for now.


Hope this helps?


Regards from a summery Johannesburg in South Africa!


Benjamin."

"Benjamin,

Thank you for yo

"Benjamin,

Thank you for your suggestions. I believe the fuel pump rebuild was done correctly for two reasons, first the problem did not change from before the rebuild to after the rebuild. And, secondly when the boat is running it runs terrific. I have tried this experiment. I have another person go with me, after sitting for a while I have the other person open the bilge compartment, I start the boat and accelerate, as the engine begins to die, the other person pumps the primer bulb until stiff, the engine will run fine after that. This leads me to believe I am sucking air somewhere between the tank and the fuel pump. What do you say?"

"i would ck your fuel delivery

"i would ck your fuel delivery system,and inst a new,quality,...primer bulb."

i agree with everything thats

i agree with everything thats been said...make sure your gas lines are 3/8 inch and not 1/4...look closely at all the gas fittings for wetness..if gas can get out then air can get in....borrow or buy a 6 gal fuel tank and run on it with another hose and bulb and see what happens...got a boating friend with a rig you can try?

"Heya'll,

I'm with

"Heya'll,

I'm with the others here. Isolate the the issues one at a time...

What's the inner diameter of the fuel line? It could starve under harsh acceleration if it's 1/4". Yet my 115 runs sweet with a 1/4" @ WOT.


Firstly, loan another tank, use your current fuel line.

Then, new fuel line, your old tank.


Good point to start from.


It's still hot & summery!!!


Keep us posted!"