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40hp Evinrude running away

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BoatBud

New member
I have a 1990 Evinrude. It will start ok and idle for a few minutes then takes off running wide open. I know the reason it is, bucause there os to much fuel in the carbs. I shut off the key pull the fuel line and have even pulled the plug wires and it keeps running till the carbs run out of fuel. My Question is why is it getting so much fuel. It had a VRO pump on it with the oil side disconnected and the fuel side went bad so i replaced it with a standard pump for that year. Thinking something was wrong with the carbs i took them apart and cleaned them. Is there a chance i didnt mix the oil right? (50/1) Should i try rebuilding the carbs? maybe a float is sticking? This is driving me nuts. Bud
 
hi . your engine keeps on running after you have turned off the ignition and pulled the plug leads because its running on pre ignition. either you have the wrong heat range plugs [plug tip glowing red] or you have glowing ember of carbon in one the combustion chambers. .continually running this engine out of control will burn a hole through a piston.
 
tobym said:
hi . your engine keeps on running after you have turned off the ignition and pulled the plug leads because its running on pre ignition. either you have the wrong heat range plugs [plug tip glowing red] or you have glowing ember of carbon in one the combustion chambers. .continually running this engine out of control will burn a hole through a piston.
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According to his post, it's running away at idle. Ignition powered up. Not dieseling.
 
From the original post>>>>>>It will start ok and idle for a few minutes then takes off running wide open<<<<<
tobym has a good post Thermo runaway,You may want to check the plugs to make sure there the right plugs. Then inspect the pistons for excessive carbon buildup.Clean them and do a decarbon after their cleaned while the engine is running.
 
Thank you for all the info. Let me give you some info i found out. First the motor ran fine till the fuel pump went bad. It was a VRO2 and not having the money to replace that, sence the oil side was blocked off, i went with a regular pump and thats when the problem started. I talked to and Evinrude mech. sense my last post and he told me he has had the same thing happen to him and it was a case of the motor running very lean, air getting in somewhere. I rechecked all the hose connections and replaced the gaskets on the carbs sence i removed them to clean them. It seam to have fixed the runaway problem but now i have a nother one. It runs all over the place and i cant keep it running. It has to be something i did wrong changing the fuel pump or cleaning the carbs. If it was running fine before the pump went bad it should run fine after i changed the pump, but it doesnt. Bud
 
Where and how is the regular pump mounted ----------Post a picture perhaps.------------------------What did you do with the VRO pulse port ???
 
Hey raceone thanks for the reply. I mounted it where ther regular pump would go on the side of the motor where the 2 bolt holes and vac. hole are. I pluged the pulse limiter hole with a brass plug with a little bit of pipe dope on the threads. I just had it running again and it will run at half and WOT but thats it. If i try to pull back any lower it stalls. I have to have it about half to even start it. Bud
 
I think it was clearly stated that he used a pre 83 ( or a special 48 / commercial pump ) standard OMC fuel pump that mounts on the port side #1 cylinder !!!
 
I have a 1988 40HP doing the same thing. Do a compression check. Mine was 120 on cylinder one, 90 on cylinder #2. You can pull the wire off #2 and it runs the same, #2 is not running, and if 2 does start to work = run away, carbs are adjusted wrong to compensate for bad idle = lync and sync = timing and carb throttle plate. Drove me nuts. Step 1 = compression check, I made it step 20. Bad power head, one cylinder not firing because of bad compression. I cleaned it with sea foam compression went down on #2 and up on #1 (125/85) was 120/90. The rule is no more then 10-15 PSI difference or 120/110 is good.
 
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