Fuel in exhaust 1986 Yamaha Pro V 150

Sven L

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Apr 30, 2012
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I just had my Wellcraft 20' put in the water two weeks ago. Died on me after about four miles from bad gas (my diagnosis). I sprayed the carbs, got 93 octane and ran it off of a five gallon gas can with a bottle of carb cleaner and she ran fine. I had her out flounder fishing a week ago and she ran great. Two days ago I go down to the marina to start her up and let her run a bit and i notice fuel rising to the surface from the exhaust. Now I know there could be a couple of things going one here. My gut feeling is she's running too rich due to a mistaken turning of the jet screw on the lower carb when she came out of winterization. My question is would this cause the gas out of the exhaust and second is any one know how to adjust the jet screw? I don't want to over adjust and have it run lean (a worse condition)

Thanks for any assistance. I'm the occasional weekend mechanic so I don't have all that much knowledge....enough to get in trouble I guess....just cant afford the marine mechanics!
 

robert graham

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Apr 16, 2009
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Re: Fuel in exhaust 1986 Yamaha Pro V 150

Since you had just started the motor, then the choke or other mixture enrichening device was probably still on and that rich gas mixture just exited out the exhaust/prop. Take it down the river, run it wide open to warm it up and blow out any rich gas residue, then check the water for gas. It would probably help to drain each carb float chamber to get rid of any water or debris from sitting up. Should be a drain screw on bottom/side of each float chamber. Good Luck!
 

99yam40

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Sep 7, 2008
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Re: Fuel in exhaust 1986 Yamaha Pro V 150

Check fuel pumps to see if they are leaking
 

Sven L

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Apr 30, 2012
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Re: Fuel in exhaust 1986 Yamaha Pro V 150

Thanks.

I drained out all my bad gas, filled the tank with new gas and went out on Sunday. Still had the same problem of bogging down one or two minutes at WOT. I was all set to head back to dock and forget fishing but we decided to run it at just enough to plane her out and just go slow. Sure enough by the end of the day she was running beautifully at WOT all the way home (about 40 minutes)! I guess whatever was in the bad fuel (gunk, water, whatever) just blew itself out. Of course now that that problem worked itself out my red oil light comes on. Looks like i'm not getting a transfer of oil from my reserve tank to the main tank on the engine. I'm not that concerned as this year i didn't totally clean out the reserve tank as I normally do so I have a funny feeling its the little white inline oil filter thats clogged. I'm just happy its not bogging down anymore on me.

Thanks again.


Sven
 

99yam40

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Sep 7, 2008
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8,851
Re: Fuel in exhaust 1986 Yamaha Pro V 150

good to hear it is running OK again but
In the future if cylinders are running lean because of plugging of some kind, you can and will destroy a motor by keeping running it that way.
may be a good idea to check compression to make sure all is good still
 

R Socey

Chief Petty Officer
Joined
Jan 9, 2011
Messages
501
Re: Fuel in exhaust 1986 Yamaha Pro V 150

When your red oil light comes on, doesn't the rev limiter engage?
 

Sven L

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Apr 30, 2012
Messages
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Re: Fuel in exhaust 1986 Yamaha Pro V 150

It didn't and that does concern me. Two years ago when i had a clogged oil line it did engage. I don't fully remember but I thought that once the red light for low main oil tank came on that simultaneously the engine will reduced power to not allow more than like 2000 RPM. If I'm correct in that, what could cause such an important warning system to fail?
 
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