225VMax rough idle and poor performance

[ransboat]

Have a VMax VX225TLRY that idles rough through all RPM ranges and will not top out. I have replaced/serviced the fuel system including all filters,had injectors cleaned/serviced/tested by flagship marine (all good),replaced all three low presure fuel pumps (this fixed my last problem of hard starting and occasional stalling). Current problem started all of a sudden mid week on a fishing trip. I have checked the plugs,caps and installed a new O2 sensor. Starts with no problem, smokes a little. No qualified Yamaha service techs within 250 miles so I am trying to repair the system myself. Rodbolt, you have helped me in the past with great results. Any help from anyone would be appreciated.

 

[cousinabe]

Re: 225VMax rough idle and poor performance

have you serviced your vst filter #23.
I have also had issues where my pressure regulator screen needs to be cleaned as well #13
http://www.boats.net/parts/search/Yamaha/Outboard/2000/VX225TLRY/FUEL INJECTION PUMP/parts.html

are you maintaining 35psi off the vst schrader valve?

 

[ransboat]

Re: 225VMax rough idle and poor performance

I put a new filter on the high presure fuel pump and cleaned the presure regulator filter. Fuel presure checks out good. I have pretty much gone through the entire fuel system from the primer bulb to the injector filters. Thinking it might be something on the ignition side, however not sure how to test all the components with basic tools. I did put new spark plugs in 4 months ago and checked the spark plug caps. The way the engine went from running great to having current problem all of a sudden mid day after running the lake all morning has me confused. It is running like a cylinder is not firing and a plug fails. It is also running the same whether it is in neutral, idle,wot or in gear. The engine has stalled a couple of times when at idle.

 

[99yam40]

Re: 225VMax rough idle and poor performance

hopefully you have the Yamaha service manual for your motor that gives the step by step procedures for testing the ignition system.

If not here is some reading for you on testing CDI units that might help you

http://www.outboardparts.com/troubleshooting/troubleshootinghelp.htm

 

[rodbolt]

Re: 225VMax rough idle and poor performance

your describing classic fuel system issues.
the ign system is pretty much dead nuts reliable and simple to test.

 

[ransboat]

Re: 225VMax rough idle and poor performance

Thanks. I will recheck the fuel presure and run some basic ignition test. I do have a sevice manual and thanks for the links.

 

[rodbolt]

Re: 225VMax rough idle and poor performance

what ya gotta do is stop. I dont care if you put a plug or a lift pump in yesterday,if it went bad today its simply bad.
test spark test compression fix the fuel system.
this is where the diagnostic test lamp,a KV tester and the O2 sensor test harness and a muti meter would come in handy.