1999 Yamaha ox66 150 low and rough idle/ stall with fuel/oil in exhaust

Heybethea

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Jul 4, 2013
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Gentlemen, I'm looking for some advice on a problem I'm having with one of my twin 150s that began a couple weeks ago. It idles rough and stalls....always cranks back up but idles low and stalls often. Also I can smell/see fuel and oil in the water while flushing the engine. I have changed spark plugs, fuel/water seperaters. Any advise on where to look would be appreciated, Thanks- Josh
 

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jdupree

Petty Officer 2nd Class
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Aug 11, 2006
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185
Re: 1999 Yamaha ox66 150 low and rough idle/ stall with fuel/oil in exhaust

Have you ever changed your LP pumps? If so, when? If not, that would be the place to check. With the fuel lines still hooked to the pump, unscrew it from the block and put your hand behind it. Pump your primer bulb and if you feel fuel there you go.
 

Capt Ken

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Jul 30, 2002
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2,269
Re: 1999 Yamaha ox66 150 low and rough idle/ stall with fuel/oil in exhaust

Problem is, he will need to remove his VST tank to get the LP pumps off. But those pumps is where I'd look first along with checking my fuel pressure. Also if the needle and seat is leaking, the over flow from the VST tank can cause those symptoms.
 

jdupree

Petty Officer 2nd Class
Joined
Aug 11, 2006
Messages
185
Re: 1999 Yamaha ox66 150 low and rough idle/ stall with fuel/oil in exhaust

Problem is, he will need to remove his VST tank to get the LP pumps off. But those pumps is where I'd look first along with checking my fuel pressure. Also if the needle and seat is leaking, the over flow from the VST tank can cause those symptoms.

Correct. Just remove the 3 mounting bolts that hold the vst and slide the tank over to the side.

When my lp pumps went my symptoms were the same as the poster.
 
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