Warm Motor Shutdown

[k-rob]

I'm new to the forum, so I'm looking for a little help. I have a 2005 Merc. 40 horse 2 stroke 2 cylinder outboard that is causing me a little heartburn. I was having trouble with the motor dying at idle last year. I rebuilt the carburetor, and it took care of that issue. However, I took the boat out on the water and had a different issue this weekend. I idled the boat out of the marina, and things seemed to be working fine. As I hit the open water, I throttled up to a plane and the motor ran good for about three or four minutes. Then it just shut down just like it ran out of gas. I was able to restart the motor, but I could not throttle up. I could only keep it running at just above an idle and limped my way back to the dock. After getting the boat home, I hooked it up to the flaps and it fired right up. I let it run at about half throttle for a while, and it shut down again. Before I start throwing money at a fix, I'm just hoping someone can tell me I'm on the right track. I would imagine there is something wrong with the fuel delivery, so my first course of action is to inspect all fuel lines leading from the tank to the carb to check for any debris or air leaks as well as replacing the fuel filter. However, if I find nothing there I am not sure what order I should check things. Guessing the fuel pump then coil. Although, I am obviously getting spark since the motor will run at low speeds when I experience this shut down. Am I on the right track? Ideas?

 

[GA_Boater]

Welcome aboard.

First thing - It is not a good idea to run at high RPMs on muffs.

Sounds like fuel to me. Fuel pump diaphragms stretch over time and have trouble keeping up a good fuel supply. I know it's shotgunning, but a new diaphragm wouldn't hurt and not expensive.

I would also re-check the float setting in the carb.

 

[k-rob]

Thank for the welcome, and thanks for the words of advice. I’ll focus more on the float adjustment and a sticky needle since I just replaced the diaphragm when I rebuilt the carb at the end of last year.

 

[GA_Boater]

I didn't look up your motor, so the pump stuff was based on a separate pump and carb.

Try replacing the filter first. And some fuel hoses between the tank and motor like to come apart on the inside. The liner pulls away from the rubber and slows down the gas.

 

[Silvertip]

Does this motor run off of a portable fuel tank? If so, before you launch down a totally unnecessary path, make sure the vent on the fuel tank is open. Did you happen to notice if the primer bulb on the fuel line was sucked flat when the engine died? If so, that is the likely issue or there is an obstruction between the bulb and the pickup in the tank.

 

[k-rob]

The motor runs off a fixed tank. It is mounted on a 16 ft.Bass Tracker aluminum boat. I am definitely going to take the hoses off and will probably replace them all the way up to the filter. I will also replace the filter. The primer bulb stayed tight all the time. I was also thinking I may have had a ventilation issue as well, so I loosened the gas cap enough to let some air in the tank, but that did not help.