RPMs bouce back and forth from 3300 to 2500 on my SWS 250

[Bob Finch]

This boat has twin 250 Salt Water ox66 98'. The port engine will join other engine when at mid range say 3300 rpms but then after a few seconds the port engine will drop to 2500 rpms, boat speed will drop and then after 5 secs it will go back up to 3300 rpms and boat will speed up. This cycle continues for a while. Only happens in mid range. If I go to 4000 both engines in sync and no problems or samething on low end. All fuel supply, plugs checked out. Wondering if sounds like fuel pump problem?

 

[John from Madison CT]

Re: RPMs bouce back and forth from 3300 to 2500 on my SWS 250

Did you check/clean the O2 sensor? What maintenance have you done to it and items like the VST filter?<br /><br />Rodbolt: Are you proud of me?<br /><br />John

 

[Bob Finch]

Re: RPMs bouce back and forth from 3300 to 2500 on my SWS 250

Cleaned O2 sensor and replaced plugs, still have the rpm problem. I will now do VST filter, that seems a little more complicated, not sure? thanks

 

[John from Madison CT]

Re: RPMs bouce back and forth from 3300 to 2500 on my SWS 250

How about also replacing the regular fuel pumps? They are cheap and part of normal preventative maintenance.

 

[rodbolt]

Re: RPMs bouce back and forth from 3300 to 2500 on my SWS 250

hello<br /> aside from all the VST and pump maint how did you clean the sensor and did you test it when done?<br /> sometimes they just die.<br /> buit it does sound fuel related. however its possible the TPS is flacky. observe the ignition timing while its surging<br /> but you also should test the O2 sensor with a voltmeter and the tech bulliten. do not use the bulletin with the flame test. it does not work.