2004 Yamaha 150 VMAX stalls out at half throttle

[Goober2011]

My 2004 Yamaha 150 VMAX 2 stroke has been stalling out when it gets to half throttle. The boat cranks fine and idles fine but shuts down if you get to half throttle. Fuel pump has been replaced and that was not the problem. Anyone have any ideas?

[Bob Gilvary]

Try a 6 gallon remote tank and see if the problem continues. Investigate problems more before you throw parts and money at it.

What's the model number?

[SparkieBoat]

I agree with bob, dont throw parts at it, them fuel pumps are pricey.

[pspear43]

same here...have a 2003 225 VMAX Saltwater Series...runs fine above 3000 and below 2000 RPMs, but in that range it stalls out and runs real rough. Any thoughts?

[Bob Gilvary]

My 2004 Yamaha 150 VMAX 2 stroke has been stalling out when it gets to half throttle. The boat cranks fine and idles fine but shuts down if you get to half throttle. Fuel pump has been replaced and that was not the problem. Anyone have any ideas?

Aside from using a remote tank to possibly isolate the problem to the engine or boat, you might want to look into your control box for a possible wire from the ignition shorting out when the throttle is in the half way position.

[Goober2011]

Try a 6 gallon remote tank and see if the problem continues. Investigate problems more before you throw parts and money at it.

What's the model number?

Thank you for the suggestions. I will try both, the model number is OX66.

[Bob Gilvary]

OX66 is not a model number.

[treblemaker]

My 2004 Yamaha 150 VMAX 2 stroke has been stalling out when it gets to half throttle. The boat cranks fine and idles fine but shuts down if you get to half throttle. Fuel pump has been replaced and that was not the problem. Anyone have any ideas?

I have the same model, but from 2003, and it's doing the exact same thing. My story is a little bit depressing, and somewhat complicated, but I'll try to keep it short. I bought a boat off a guy that had a 1999 Yamaha 150 VMAX OX66 TPR, model number DX150TLRX. It got inspected, had full compression but needed a water pump. Lesson learned: never buy a boat that you're not able to test in the water for whatever reason. I bought the boat anyway at a reduced price and took the responsibility of fixing the water pump at my own expense. OK, so two weeks later, water pump is fixed and I put the boat in the water. As I accelerated, suddenly the throttle would cut. Then, 30 seconds later, the engine stopped firing on all cylinders and crapped out. Turns out there was extensive corrosion inside the motor, crankshaft, pistons, contacts... everything was water damaged and two of the injectors stopped injecting altogether. So, after months of... (insert long story here) ... I bought a 2003 Yamaha VMAX 150 HPDI OX66, model number VX150TLRB. It's basically the exact same motor, 4 years younger, with a regular foot/prop. All I did do it was have the garage swap out the foot for the 1999 dual prop out of simple preference.

So I get out on the water and after 5 minutes of normal operation, you guessed it, the throttle starts cutting out at around 2000 RPM, but runs fine at under 1700. Now what are the chances that I have the same problem with both motors? Water in the gas tank perhaps? I had the tank completely pumped out to empty and then refilled it. The red water indicator in the fuel filter has not moved up. I even tried running the motor on a separate gas tank and it still did the same thing. I changed all the spark plugs, again to no avail. Could it be my dual prop, somehow causing too much resistance and forcing the engine to cut out? Other than the gas tank, it's the only common link between the old 1999 motor and the replacement. But the garage checked out the gearcase and it was turning fine. I'm all out of ideas.

So what was your issue after all? Did it get figured out? Does any part of this story sound familiar to anyone?

[SparkieBoat]

most likely you all are having fuel issues. change all filters, have injectors cleaned/tested, clean out VST and screen on bottom of fuel pump, flush fuel rail, check fuel rail pressure while problem is occurring, check all sensors and valves including the fuel pressure control valve. I assume you have checked tank for clean pick up and vent, and replaced all lines and checked all connections and checked/replaced bulb, and checked spark and compression.

[99yam40]

Monitoring fuel pressures while problem is happening will give you some idea if there is a problem on the fuel pumps or restrictions in lines or filters. But if you run it long with a lean fuel problem you will have major mechanical problems also

[treblemaker]

most likely you all are having fuel issues. change all filters, have injectors cleaned/tested, clean out VST and screen on bottom of fuel pump, flush fuel rail, check fuel rail pressure while problem is occurring, check all sensors and valves including the fuel pressure control valve. I assume you have checked tank for clean pick up and vent, and replaced all lines and checked all connections and checked/replaced bulb, and checked spark and compression.

Thanks for the help. It is definitely a fuel issue. Fuel pressure drops dramatically at the gas tank pump. I don't know what the chances are that the same issue would happen on two motors, but it did. Back to the shop it goes.

[treblemaker]

Thanks for the info.