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1994, 40 HP, 2 stroke problem.

J

jc sparks

New member
I have a 1994 Merc 2 stroke, 4 cylinder. Every once and a while when I am at full throttle it feels as if it is starving for fuel. If I leave it at full throttle it will lose RPM until it stalls. It does not chug or sputter, it simply looses RPM. If I throttle back to 1/4 throttle or so it will continue to run. I let it stall the other day, I went back and pumped the primer ball and It started rite up just like it has when this happened in the past. Then I was able to run full throttle back to the dock (10 minutes or so full throttle) no problem.

I have done mechanical work all of my life so I know my way around most anything mechanical. This past spring I rebuilt the carburetors and fuel pump and went to Florida. It ran perfect for 14 days and then one day I am motoring back to the dock and I experienced this problem for the first time. It started back up and I went to the dock. I looked at everything and decided to replace the primer bulb and fuel lines just encase. I go out every day for 4 more days and then it does it again.

So today I drain and pull the tank to see if there is something in the pickup. The tanks is clean with nothing in the lines. It all looks just fine.
I am going to take the carburetors and fuel pump back off and go through them.

What do you think about this? Thanks for any input JC
 
Might be bad check valves in the bulb (or an air leak before the fuel pump). Had that happen to me once--drove me nuts. Can you try another line and bulb?

Jeff
 
There is a new line and bulb on it. The only place I can see that could be a possible air leak before the fuel pump is to disconnect on the fuel line. If has never dripped though.
 
I tested the ball with a brake bleeder (pulled vacuum ) and it held the vacuum so it is not leaking. I ordered a new fuel line disconnect. The thing that makes the disconnect suspect is it runs like a top for a long time then out of the blue it will lose RPM / power like you pulled the throttle back. This could be from the ball and fuel line moving around from wave action to move the disconnect just enough to let it suck some air. I'm still working on it. JC
 
Could be it's sucking in air there. I eliminated that connection on mine after having problems with it in the past.

Jeff
 
I got the new fuel line disconnect and it sure fits a lot tighter that the old one. I hold some hope that it was the problem. I will try to take the boat out on Erie this coming Monday and give it a good hard test. I will report back. JC
 
jc sparks said:
I got the new fuel line disconnect and it sure fits a lot tighter that the old one. I hold some hope that it was the problem. I will try to take the boat out on Erie this coming Monday and give it a good hard test. I will report back. JC
Click to expand...

I'm having the same problem...you got any updates..?
 
I just got back from lake Erie, I ran it wide open throttle for 25 minutes with no problem at all. I have to believe it was the fuel line quick disconnect. The old one had a few small chips out of the seal and it was sucking air every once and a while. JC
 
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