Yamaha 250HP V76 SWS II PLease Help! Desparate!

[TROUTN]

Hello I have a 2000 Yamaha 250hp EFI V76 SWS II motor with 230 hrs and an intermitant problem. <br /> Goes like this-Start up motor let idle for 10 to 15 minutes, go to give throttle and at about 35 to 37 rpm's just before the boat will level off to plane it just shuts down and runs very rough and will not take throttle. If I pull back on the throttle it will calm down and then when I go back to the gas it shuts down again. If upon shutting down I leave the throttle advanced the motor will run very rough and die completely after a minute or so. The problem is it doesn't do this all the time. Sometimes it will start and take throttle and run beautiful. <br /> If the motor doesn't die the first time upon giving it throttle it will run great. <br /> I brought it to a yamaha dealer and first he said the VST filter was clogged and he cleaned it. No change in the way it ran. He also did compression (100 ea)and checked the rest of the fuel system found nothing wrong. Any suggestions??

 

[ida71]

Re: Yamaha 250HP V76 SWS II PLease Help! Desparate!

Definately sounds like a fuel starvation problem. I assume it is not over heating & is using oil correctly, in which case you can rule out seizure. If the dealer checked the fuel system on the engine, then I'd check your fuel supply system. If its running from an internal tank on the boat, I'd get a portable tank complete with a different connector hose & try it then. You can also try having someone manually pump the primer bulb while the engine is running, it should not go soft after the engine starts. You should get one squeeze before the bulb goes completely firm when the motor is running.<br /><br />If you can pump it continuously when the motor is running, it would imply an air leak in the fuel supply system, use the portable tank next to see if its in your installed system or somewhere in the engine !<br /><br />Chris W.

 

[rodbolt]

Re: Yamaha 250HP V76 SWS II PLease Help! Desparate!

test all your low pressure pumps. I reccomend replacing them every 3 years just a a routine maint issue. if the VST has no fuel to pump it wont pump anything. thus causing it to die.<br /> good luck and keep posting also clean your o2 sensor. its way over due as well

 

[TROUTN]

Re: Yamaha 250HP V76 SWS II PLease Help! Desparate!

While the motor was dying I had the cover off and was only able to squeeze the bulb one time before it was completly hard and this made no difference in the way the motor ran once I squeezed the ball. I'll tell the dealer about those low pressure pumps and the cleaning of the O2 sensor

 

[TROUTN]

Re: Yamaha 250HP V76 SWS II PLease Help! Desparate!

Rodbolt the dealer keeps telling me he can hook a laptop up to the motor while it is running and that will tell him what is wrong. Is this true or not?

 

[TROUTN]

Re: Yamaha 250HP V76 SWS II PLease Help! Desparate!

Dealer just called me and told me that he believes I have a low voltage problem and that is what is causing the motor to die on an intermitant basis. I don't know if I believe him or not. He said if the voltage drops to 11.5 the motor will not run right?? True or not?? If it is low voltage to the motor why have I never had trouble starting the motor?? Please help.

 

[rodbolt]

Re: Yamaha 250HP V76 SWS II PLease Help! Desparate!

I think you need to find another dealer. I dont belive the 2000 model OX66 motors had laptop capeabilities. there is a diagnostic test lamp that can be installed at the oil tank connecter that will give an indication of the TPS and some of the other sensors. most the efi problems I deal with are fuel pressure related. that motor will run quite nicely at 11.5 volts about 9 it will shut down due to the high pressure pump cant run anymore. do you have the multifunction speedometer or a voltmeter installed? the O2 sensor can make it do funny things at idle and reduce WOT as well as smoke a piston.

 

[TROUTN]

Re: Yamaha 250HP V76 SWS II PLease Help! Desparate!

I did not think that the voltage was the problem after all the motor ran fine for 2 years with the same electronics draw and accessory draw now all of a sudden the draw is too much doesn't add up. The lowest I have ever seen the voltage is 11.7 volts. I do have the multifunction speedometer and it has never given me a warining or anything. Is it easy enough for me to change the O2 sensor? I called Yamaha directly and they are agreeing with the dealer that it is a voltageproblem.

 

[rodbolt]

Re: Yamaha 250HP V76 SWS II PLease Help! Desparate!

its simple to test. next time its running shift the mode to the BATT position and seewhat it reads. buy the test harness for testing the o2 sensor and use a digital meter. with the boat in the water and the engine running with the air box off place a finger over the airhole in the top throttle plate and watch the meter go mad. then remove the finger and watch it go the other way. if it is a low and steady voltage or high and steady odds are the sensor is bad or the draw tube is clogged or both. if you dont clean them periodically they die.<br /> the range for the o2 sensor is about .2volts to about .9 you will be looking for it to scale up and down between about .35 and about .65. if it does not there is a problem. you can also test the o2 sensor heater voltage with the sensor test harness. I still would be wary of the voltage theory and me and some of the service techs at yamaha have had sharp words over battery and voltage issues on the ox66 and especially the HPDI. most of the issues boil down to most dealers have techs that rely to much on parts changing and not enough on test and trouble shooting skills. if I tell some one a stator or an o2 sensor is bad and I replace it and it still wont work I just bought it. therefore I am very rarly wrong when I tell the marina or customer what part is bad. I have had my own business now since about 92 and I contract my services to various dealerships in the area. my advice is to ask to see the fuel systems training guide as well as the gold bar that indicates the tech has attended fuel systems. EFI is so very simple that most people get lost.<br /> good luck and keep posting.<br />ps that sensor is about 350 bucks

 

[TROUTN]

Re: Yamaha 250HP V76 SWS II PLease Help! Desparate!

Well here it goes. Test ran motor motor on weekend after dealer still insists that I have a low voltage problem even though he has never tested for that. Dealer also adjusted the TPS and throttle body linkage because he noticed a rough transition band?? Also left the diagnostic light attached to the motor while we were going to test it. Dealer also gave me the list of codes that would be given by the light. <br /> Results motor ran fine going out as always then we turned it off and trolled with 9.9 for 3 hours then started the 250 again and upon giving it throttle the motor shut down again. But this time the warning buzzer went and the multi-gauge oil indicator lights all were flashing. The test light started to flash 4-3 which indicates a buzzer going off. Quickly shut off engine and pulled hood inspected oiltank on motor and found it was at the low arrow mark. This I believe is my problem. Upon turning key back on to the on position without tunring the motor over you could see the pump begin filling the tank on the motor once again. Started the motor once the oil level was back up to the upper arrow and the motor ran great again.<br /> Now for the questions why have I never had the warning buzzer go off before? Why did it take hooking the diagnostic light up to make the buzzer go off? Could the light have just made the connection better? And when should the pump on the remote tank begin to refill the tank on the motor?<br /> We tested the motor with the key in the on position and motor off. I drained oil form the viwing tube on the bottom of the tank. The pump never kicks on the whole time it is draining but when the level reaches the low arrow mark the buzzer goes off.<br /> Turn the key off and back to the on position and the tank refills slowly to the upper mark. Why doesn't it fill before it gets to the low mark. Also why won't it refill even when the alarm is going off? I have to reset it with the key switch to get it top pump oil in.<br /> Another separate problem, the dealer adjusted the TPS because of a rough transition around 18 rpms he said it was at 4 volts and he adjusted it to 5 volts. Well now the transition is worse now than it ever was. If you leave the motor at 1800 rpms it sounds like it's dropping some cylinders it runs so rough. If you just power through that range of 16 18 rpms you don't notice it as much. How should this be fixed?<br /> Thanks again for your input.

 

[rodbolt]

Re: Yamaha 250HP V76 SWS II PLease Help! Desparate!

you really really need to find a dealer that knows their butts from a hole in the ground<br /> you adjust the TPS with the throttle fully closed to .5=/-.05 volts no other way to do it. any first year yamaha apprentice can tell you that with the diagnostic lamp installed their will be no oil transfer. I will tell you one more time<br /> your dealer needs to send competent motivated techs for training and you should find another dealer before they sell you a power head.<br /> has anyone tested the O2 sensor the way I described? has anyone tested the spark plug cap resistance?<br /> sounds like a lot of poking and hoping and your paying<br /> good luck keep posting but find another dealer

 

[TROUTN]

Re: Yamaha 250HP V76 SWS II PLease Help! Desparate!

Talked to Yamaha today the y confirmed what you said rodbolt that the light will interrupt the flow of oil to the tank. So I'm back to square one. I am going to try a different dealer now though. Where can I get the best yamaha manual and do all this stuff myself? Is there a number you can be reached at rodbolt?

 

[rodbolt]

Re: Yamaha 250HP V76 SWS II PLease Help! Desparate!

maybe.<br /> but first we need to back up retest run the engine and find out the symptoms again. I dont want to know what it did. I want to know what is it doing today.<br /> good luck and keep posting

 

[TROUTN]

Re: Yamaha 250HP V76 SWS II PLease Help! Desparate!

Sorry I haven't posted sooner but I was away on vacation. Great news problem solved it was the TPS!! Motor now runs better than it ever did. Ever since I owned the motor upon cold start it would high idle and while coming back down to idle it would stall.I would restart it and it would run. Even that is now fixed. The transition from low to high rpms is much smoother. Thankyou Rodbolt for pointing me in the right direction the dealer certaintly didn't. If it wasn't for your help I still would be without a great running motor. Thanks