2002 ox66 250 losing rpms over 4500rpms

[tobias pardue]

i have a 2002 ox66 250 that runs fine at lower rpms and then feels like it loses a cylinder or two as i push it harder. boat is a 27 contender with twins and other motor is fine. engine does not die only loses 200-400 rpms. i have replaced the fuel pump and the plugs, but still have the problem. model is lx250txra. any help appreciated

 

[rodbolt]

Re: 2002 ox66 250 losing rpms over 4500rpms

hello<br /> have you cleaned the o2 sensor? the sensor will make a surging problem if dirty/also check the vaporseperator filter. it has to be serviced occasionally.<br /> good luck and keep posting

 

[BRIAN03]

Re: 2002 ox66 250 losing rpms over 4500rpms

You need to watch the fuel pressure and see what it does. There are two different fuel pumps on that engine. 1. low pressure (three of them) and 2. a high pressure electric in the fuel chamber. There is a shrader valve on the fuel chamber. Watch the fuel pressure as the engine noses over. There is a filter on the bottom of the high pressure fuel pump.

 

[BRIAN03]

Re: 2002 ox66 250 losing rpms over 4500rpms

Hey Rodbolt look at the time we posted. Good Job.

 

[tobias pardue]

Re: 2002 ox66 250 losing rpms over 4500rpms

thanks guys, i have replaced all of the fuel pumps $1200 and that was not it. i would swear it is electric. someone said something about a "knock sensor" that will kill a cylinder or two if there is the slightest bit of vibration in the motor? the o2 sensor will be done tomorrow and i will post the results.

 

[BRIAN03]

Re: 2002 ox66 250 losing rpms over 4500rpms

Even if you replaced the fuel pumps I would still like to see what the fuel pressure is doing. I always say prove or disprove. I agree with Rodbolt an 02 sensor can do it. I work from easies to hardest. dont give up.

 

[seahorse5]

Re: 2002 ox66 250 losing rpms over 4500rpms

Go to <br />www.thebassguide.com/home/News/05-30-2002-01.htm<br />for an article about cleaning O2 sensors. I'm with Brian and Rodbolt on the troubleshooting. Run the motor at the problem rpm and watch the high pressure fuel reading on a pressure gauge. You can also use a timing lite on each plug wire one at a time to check ignition at that rpm. In some cases you may have to run with the airbox off, carefully, and shoot gas in each throat using a pump oil can to see if an injector is leaning out.

 

[BRIAN03]

Re: 2002 ox66 250 losing rpms over 4500rpms

Hi Seahorse I use to use a timing light all the time and I found Fluke has an rpm probe for the ignition wire it works great in the sun light. Fluke also makes a Vac/pressure adapter that works great for vac pull readings and fuel pressure reading. I agree with you on watching the fuel with a timing light. The fluke wont do that.

 

[tobias pardue]

Re: 2002 ox66 250 losing rpms over 4500rpms

well, it looks like it just might be the fuel pressure. we removed the filter and put the pressure tester in line and it ran like a champ. filter on order and will see if that does it. thanks for all the advice.