03 150 Yamaha surges after throttle is givin??

[Alpha Dog]

I`ve got a 2003 150 Yamaha fuel injected that idles great starts great and will take off good but then starts surging. whats been done so far found water in the fuel,cleaned tank replaced all filters in boat and on motor,two new manual fuel pumps, new filterand rebuild on the electric pump on the vst, new plugs,also new filters on the injectors. its firing on all six at idle and at wot. but suges from 5000 rpm to 2800 to 3000 to 5000 and so on thinking stator maybe ?? any info would be Great Thanks

[Superbender]

Have you checked fuel system with a vacuum gauge,fuel pressure at the vst.and get a voltage reading from o2 sensor.maybe you could explain better by what you meant about rebuilding electric fuel pump in vst?

[Alpha Dog]

Have you checked fuel system with a vacuum gauge,fuel pressure at the vst.and get a voltage reading from o2 sensor.maybe you could explain better by what you meant about rebuilding electric fuel pump in vst?

yeah Bender I have checked the fuel pressure and the vacuum it all is with in the guide lines.i didn`t know that a two stroke had a o2 sensor. and what I meant about rebuilding the vst was the float and needle in the vapor tank and a new filter on the electric motor sorry I should have explained that better . I was also wondering about the throttle position sensor??

[Alpha Dog]

Any ideas ?? Need Help.

[Markus]

Can you check fuel pressure when the surge happens?

[Alpha Dog]

Yes I put a gauge on it and it was pretty much steady pressure. It fluctuated slightly.

[VectorPat]

Yes it has an O2 sensor. If it is fouled it will cause it to surge, it also has a joint tube that joins the sensor to the #1 cylinder. If it is plugged it will cause the same issue.

[Alpha Dog]

Alright thanks I'll check that out and let ya know..

[Superbender]

OK just to make sure here you have more then 4lbs going into vst,vst has at least 30 to 35lbs of fuel pressure when problem occurs,and you have 3 or less pounds of vacuum.next I'm gonna ask you to get a friend to drive the boat while you mist a little premix into motor while surging occurs thru the airbox.

[Alpha Dog]

ok Fellas I`ve tried all the above plus replacing the fuel pump and pressure regulator in the vst. looks like I have a breakdown in the ignition at around 2800 to 3500 rpm stator...Brain...trigger??? I`m at a loss the new pump and all did give it a pick up but now its more noticeable that it is an ignition Break down any Thoughts Please.. Thanks

[VectorPat]

Check each cyl with a timing light and try to isolate which cylinder it is and make sure it truly is an ignition problem.

[Alpha Dog]

Alright it looks like 5&6 are miss firing only at upper rpm idling they fire just fine...any suggestion??

[Alpha Dog]

Ok I double checked the miss fires it seems like its random on all six so I'm leaning a stator or the I'm going to ohm test them tomorrow does anyone have a chart of what the should be I've been trying to find that all night the motor its a sx150 Txrb 2003 150 any info would be Thanks

[Alpha Dog]

AlLright I've Done All The Electrical Checks.. Looks Like The Throttle Position Sensor IsTheOnly Thing That The Numbers Don't Match.. Volts Ohms..WouldThatCause This Kind Of Behavior??

[VectorPat]

Explain how you are testing it. You can check them by using an old analog style meter. The needle should move smoothly along with the sweep of the TPS. If there is a dead spot you will see the needle jerk or bounce around. This is sometimes hard to see on a digital meter. You should have 5v going into it on the black and orange wire and .5v on the black and pink wires with the throttle plates completely shut. With the plates adjusted for the correct idle speed it will have somewhere around .6v on the black and pink. I dont know what the resistance should be, I only use voltage to check them.

[Alpha Dog]

Vector TheManual I Have Reads In Volts 0.48 To 5.25 And That's On The Orange And Pink Wire.. I Get 0.48 But When The Throttle Would Be Increased I Only Get 3.82 Its Like Its Dead About Half Way Up Any Thoughts??

[Superbender]

3.82 Is about right,what is the stator output?its got a high and low speed winding like a merc,rare but have seen them go bad.

[Alpha Dog]

Superbender The Stator Reads 85 To 110 At Cranking Speed.-also ive checked the pulsar coil and got 3.0 volts at cranking speed on all six pins.the crank position sensor has two pins and the volts are supposed to be by the manual 6.0 to 0.5 but I couldn't get a good reading either way not sure how to test that one or what should the meter be set at?? this thing is killing me lol..... and Thanks for the info everyone

[Superbender]

You might have to make an adapter to test stator while under load to test the stator.

[VectorPat]

Vector TheManual I Have Reads In Volts 0.48 To 5.25 And That's On The Orange And Pink Wire.. I Get 0.48 But When The Throttle Would Be Increased I Only Get 3.82 Its Like Its Dead About Half Way Up Any Thoughts??


Is your manual referring to the wires in the harness, the TPS wires(which can be different than the harness wires sometimes) or the test harness? I go by the main harness, but maybe im wrong. Just as long as there is around 5v going in and yes the voltage spread you have is correct if the TPS is off the motor. At WOT you will only get 3.7 to 4v when still mounted on the motor.

[Alpha Dog]

well Thanks for all the input Everyone!! Problem solved it was the Stator really weird how it was acting but that solved the problem..gotta bunch of new parts on it so should be good for awhile.. Lets Hope lol