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Author Topic:   Emergency Fuel Enrichment on Yamaha 90

808Boater posted 06-01-2009 08:18 PM ET (US)
In 2008 I bought a Yamaha 90-HP two-cycle outboard motor. I have about 75 hours on the motor, but it has been getting really bad gas mileage and oil consumption. It's also fouled two sets of spark plugs within 70 or so hours. I took it in to our local dealer to diagnose this. They returned the boat to me and told me that the emergency fuel valve was in the open position. They turned it to closed and told me that this should fix our fouling and bad gas mileage issue.
Would running the motor with the emergency valve on "open" (and I am assuming a very rich fuel mixture) for 70 hours cause any engine damage?
Also, should the switch be in the normal or closed position during usage? They set it in the "closed" position after I took it in. Thanks in advance for your help.
Tohsgib posted 06-01-2009 08:39 PM ET (US)
Obviously it did not cause any problems before. I would be weary of the future but you have warranty. Go for it.
maineidyl posted 06-01-2009 09:36 PM ET (US)
I just had a problem with this valve on my 1996 Yamaha 90. The motor would sound like it was starving, and only run around 1,500-RPM. It would not run under load but would idle perfectly. I tried to fix it by trial and error. I did the fuel ball. Then new plugs. Then emptied the tanks. Each time it still would not run under load. Finally took it to a mechanic who I grew up with, and he said I was the fuel enrichment valve. Cleaned it, put it back together and runs perfectly. The strange part is, in the normal position it enrichens the mixture, like the old chokes on a carb, a spring like device heats up and then closes as the motor warms up. I was actually drowning the engine not starving it. The mechanic told me to turn it to off if it happens again and he will replace the valve. Mine is back to the factory setting and running perfectly. If under warranty I would have it fixed and run it how it supposed to be. Sorry for the drawn out story. Just wanted to provide the little information I had.
Tom
Chuck Tribolet posted 06-01-2009 09:39 PM ET (US)
That's not a drawn-out story, that's good info for Yammie
owners.

Chuck
jimh posted 06-01-2009 10:19 PM ET (US)
Many OMC motors have a similar valve which can be operated electrically by a remote button (often called a CHOKE button) during starting, and also operated manually by opening a valve or petcock. One spring at engine initial start up for the season I found my motor was running very poorly and was difficult to start. The cause was the accidental opening of the manual enrichment valve. As soon as I closed the valve to its normal operating position, the engine began to run normally.
ASIDE: My expert OMC mechanic diagnosed this condition over the telephone immediately when I described to him the circumstances and the engine behavior. I think it happens frequently, at least that's my inference, as he seemed to be very familiar with the cause and effect of the enrichment valve being open. I believe the intent is to aid in starting under certain circumstances when the electric valve has failed.
tedious posted 06-02-2009 06:40 AM ET (US)
The OMC primer system has a solenoid that opens when the keyswitch is pushed in - this lets a squirt of fuel from the fuel pump shoot directly into the manifold, after the carbs. The solenoid also has a manual valve that is used if your battery is dead and you need to rope start. This valve is a small red lever on the side of the primer solenoid - after 1990 or so, it also included a Schrader valve that lets you shoot fogging oil or decarb fluid into the engine without taking off the intake silencer. The valve is open when at right angles to the solenoid body, and closed when parallel to it.
The manual valve does have a detent, so it clicks closed, but it's not a very strong one. It's easy to knock the valve open; I'm sure a lot of people do it when using the Schrader valve.
Tim

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Author	Topic: Emergency Fuel Enrichment on Yamaha 90
808Boater	posted 06-01-2009 08:18 PM ET (US) In 2008 I bought a Yamaha 90-HP two-cycle outboard motor. I have about 75 hours on the motor, but it has been getting really bad gas mileage and oil consumption. It's also fouled two sets of spark plugs within 70 or so hours. I took it in to our local dealer to diagnose this. They returned the boat to me and told me that the emergency fuel valve was in the open position. They turned it to closed and told me that this should fix our fouling and bad gas mileage issue. Would running the motor with the emergency valve on "open" (and I am assuming a very rich fuel mixture) for 70 hours cause any engine damage? Also, should the switch be in the normal or closed position during usage? They set it in the "closed" position after I took it in. Thanks in advance for your help.
Tohsgib	posted 06-01-2009 08:39 PM ET (US) Obviously it did not cause any problems before. I would be weary of the future but you have warranty. Go for it.
maineidyl	posted 06-01-2009 09:36 PM ET (US) I just had a problem with this valve on my 1996 Yamaha 90. The motor would sound like it was starving, and only run around 1,500-RPM. It would not run under load but would idle perfectly. I tried to fix it by trial and error. I did the fuel ball. Then new plugs. Then emptied the tanks. Each time it still would not run under load. Finally took it to a mechanic who I grew up with, and he said I was the fuel enrichment valve. Cleaned it, put it back together and runs perfectly. The strange part is, in the normal position it enrichens the mixture, like the old chokes on a carb, a spring like device heats up and then closes as the motor warms up. I was actually drowning the engine not starving it. The mechanic told me to turn it to off if it happens again and he will replace the valve. Mine is back to the factory setting and running perfectly. If under warranty I would have it fixed and run it how it supposed to be. Sorry for the drawn out story. Just wanted to provide the little information I had. Tom
Chuck Tribolet	posted 06-01-2009 09:39 PM ET (US) That's not a drawn-out story, that's good info for Yammie owners. Chuck
jimh	posted 06-01-2009 10:19 PM ET (US) Many OMC motors have a similar valve which can be operated electrically by a remote button (often called a CHOKE button) during starting, and also operated manually by opening a valve or petcock. One spring at engine initial start up for the season I found my motor was running very poorly and was difficult to start. The cause was the accidental opening of the manual enrichment valve. As soon as I closed the valve to its normal operating position, the engine began to run normally. ASIDE: My expert OMC mechanic diagnosed this condition over the telephone immediately when I described to him the circumstances and the engine behavior. I think it happens frequently, at least that's my inference, as he seemed to be very familiar with the cause and effect of the enrichment valve being open. I believe the intent is to aid in starting under certain circumstances when the electric valve has failed.
tedious	posted 06-02-2009 06:40 AM ET (US) The OMC primer system has a solenoid that opens when the keyswitch is pushed in - this lets a squirt of fuel from the fuel pump shoot directly into the manifold, after the carbs. The solenoid also has a manual valve that is used if your battery is dead and you need to rope start. This valve is a small red lever on the side of the primer solenoid - after 1990 or so, it also included a Schrader valve that lets you shoot fogging oil or decarb fluid into the engine without taking off the intake silencer. The valve is open when at right angles to the solenoid body, and closed when parallel to it. The manual valve does have a detent, so it clicks closed, but it's not a very strong one. It's easy to knock the valve open; I'm sure a lot of people do it when using the Schrader valve. Tim