Yamaha 150 VMAX Just Died

[Captain Steve]

I was heading in yesterday after an awesome day of fishing. I was running about 3500 rpm's and it was calm. All of sudden the motor just dies, as if someone pulled the kill switch. When trying to restart, it just rolls as if there is no spark.

I run this boat/motor 3 or 4 times a week, and she had been running like a champ. No problems otherwise.

Any idea where I can start trouble shooting?

Thanks.

[rodbolt17]

I wonder what color it is painted?
I wonder if it has carbs?
I wonder if it is an EFI/OX66?
it could be HPDI.
why is a model number so hard to provide?

[Captain Steve]

Ox66

My apologies for not posting model. Model is OX66, with a TRP, trim and electric start, 20" drive. 2004 model.

Thanks

[rodbolt17]

that's still not a model number but it gets me close.
does the electric fuel pump in the VST turn on for 3-5 seconds at key on?
my guess is you lost spark or fuel.
first guess would be fuel.
to test the kill circuit/alarm circuit pull the stop lanyard and crank it, you should get an audible tone.
the DX150 was made from 99-05.

[Captain Steve]

Dx150tlrc

DX150TLRC - 2004

The boat is currently in the water at the camp. I will run to the camp now and I will first verify the electric pump in the VST runs for 3-5 seconds at key on. If VST pump is running at key on, I will check the kill circuit as suggested.

I will let you know what I find out.

Thank you very much.

[Captain Steve]

VST Pump

Ok, turned key over first time, there was a "tick", but pump not running.

Turned key off and back on, pump runs. So I started her up. When I rev the throttle up, she dies.

Turn key off and back on, VST pump not running. Tap on the VST tank with my knuckles and pump runs 3-5 seconds and she will start and run. But, rev up throttle and she dies.

VST pump gone out?

There is 530 hours on motor.

[rodbolt17]

possibly,but now is the time to test the supply voltage from the main relay and the ground path from the pump(blue wire) to the ECU.

[Captain Steve]

Testing Supply Voltage

Excuse my ignorance on the subject, but can you please identify the main relay on the attached PDF?

Also, can you please confirm that I should take volt meter and place one probe on the main relay, and the other on the ground path from the pump (blue wire) and verify I have voltage?

Thanks again for your help.

[rodbolt17]

test pump red wire to engine block at key on, it should read battery voltage.
if it passes move the lead from the red lead to blue with the key off.

now turn the key on,the meter should go to less than .5V for 3 to five seconds then return to about 1v less than battery voltage.

now start the motor,you should see less than .5V.

an analog meter may work better than a digital for this test.

what we are trying to determine is the pump brush assy bad? are we losing supply voltage?
are we losing the pump ground path.
two things happen when you throttle up.
it needs more fuel.
it increases the electrical load on the main relay.
if you have a bad pump or a bad connection the engine may stall.
if the VST filter is clogged it simply cannot flow enough fuel and it stalls.

[Captain Steve]

Test Failed on Blue Wire

Check red wire to engine block key on, and I get full battery voltage 14.2 volts.

Turned key off, went blue wire to engine block and turned key on, and it is showing .7 milli-volts, and VST pump will not run.


Tap on VST tank with palm of hand, and pump runs 3-5 seconds and voltage drops to .55 volts (+\-), and then goes to 14.2 volts (+\-).

Start motor and we are running engine with 3.14 volts at idle speed.

When I idle up the throttle it it drops to 0 volts and dies.

Your help is much appreciated.

[rodbolt17]

two things, showing the .7mv and the fact that by tapping on the pump show an open circuit between the pump red wire and ground.
3.14 is about right at idle.
what you are measuring there is the voltage drop acroos the pump brushs and the low speed pump resistor.
when the engine stalled you should have read about battery voltage.
means either the main relay turned off or the pump opened circuit.

[Captain Steve]

main relay turned off or the pump opened circuit

Thanks Rodbolt,

You stated "means either the main relay turned off or the pump opened circuit".

Again, excuse my ignorance on this subject, but where is the "main relay" located? Would you recommend replacing the main relay? Is it possible to further test the relay?

As far as the open circuit between pump red wire and ground, is the pump grounded to the block thru the bolts which attach the VST to the block, or is there a specific ground wire I need to be looking for?

Is it possible there is a problem with the connection between the red wire and the VST pump itself?

How would you recommend I further isolate the problem, or should I look at replacing the relay and or pump?

I know the pump is rather expensive, but I have no idea on the price of the relay, or the relay part number.

Thanks again for all your help.

[Captain Steve]

Replacing the VST Pump

I have a buddy with the same motor that is blown and sitting inside his barn. He said I can have the entire VST tank and pump if I want it.

If I replace the VST pump, will this correct my problem?

[99yam40]

maybe or maybe not.
depends on what the problem is and if his pump is good

need to find out if 12+ on the red stays when the problem shows up.
If the 12v Pos goes away replacing the pump will not fix it.

something is going away or brushes or connectors making internmentant connection
+ or ground, check all connections

[Captain Steve]

Voltage on Red Wire when Problem Occurs

Well, I am no long able to tap on the VST Tank to enable the VST fuel pump to run, so I can start the motor, and see if we are maintaining 12+ volts when the problem occurs.

As far as checking connections, I have traced the red/Blue wire back to where it ties into a harness of wires behind the VST, and all looks good. Should I pull the VST tank and trace down the entire harness?

Are there other wires I should be looking for?

Your help is much appreciated.

Thank you