Evinrude 40hp stalling problem

[JrMechanic070]

Hey guys, I have a evinrude 40hp outboard that I'm trying to get running. I took it out monday and it ran perfect at all speeds. Then I took it out on tuesday and it started having problems. It runs great at idle, and great at full throttle, but it doesn't want to run at mid range..!? If you jump it up from idle to full throttle it runs great, and if you bring it down from full to idle it will work. But if you accelerate slowly it starts to sputter and shake and die around mid throttle. The same thing if you bring it down from full it mid throttle. It just wont run right at mid range. I cleaned out both the carbs. Completely disassembled them, sprayed them out with carb cleaner, then blew them out with a compressor. I tried adjusting the screws on the top of the carbs with no results. The engine has 140 psi even on both cylinders, and great blue spark on both cylinders. It has brand new fuel lines and bulb from the tank to the motor, and it has new ethanol free gas. I'm really stumped here, and I need to get it running by saturday. Any help at all will be greatly appreciated. Thanks

 

[jakedaawg]

Model # please.

 

[JrMechanic070]

I don't have the model number because the plate on the side is missing. I have the serial number if that would help? Thanks

 

[urbanredneck]

Know what year it is at least? We can find out the model number based on year, horsepower, ignition style, etc....

 

[JrMechanic070]

Ok sorry, Its a 1989 Evinrude 40hp.I tried to upload some pictures but it wouldn't let me. Thanks

 

[oldboat1]

any chance of water in the tank? vro or pump issue, filter issue....

 

[JrMechanic070]

I don't believe there's any water in the tank or filter. I'm going to take it to the ramp this afternoon I'll trying hooking up an auxiliary tank with fresh gas and see if it makes a difference. The engine has had the VRO disconnected, I mix the gas 50:1. Do you think the fuel pump could be the problem considering it runs great at idle and wide open? Any other suggestions or things I should try?? Thanks, Mark

 

[Silvertip]

Fuel pump is not the issue if it runs fine at wide-open throttle. You apparently do not have the mixture screws adjusted properly as those must be spot on for best idle as well as "transition" which is the period where you get off the low speed jets and onto the high speed. You cannot just twist away on these screws. They require very fine adjustment changes and then a period for the engine to stabilize before adjusting again. You may also have to do a "link&sync" which a rather lengthy process that synchronizes throttle opening with spark advance. This is not something anyone will type for you here. You need a service manual and you must perform the complete procedure. Starting in the middle is not an option.

 

[jakedaawg]

I actually did type it out once in here. A link and synch is probably the answer.