I've got twin 2000 0x66 250's. One of them won't stay running at idle. What's weird is that if it is at idle in gear, it will run, but in neutral it coughs a few times then craps out.
When first starting from a cold start, I can start it, it idles OK for maybe a minute, then starts to cough and sneeze and stalls. Starting it after that results in pretty quick stalling.
I can't say for sure, but I believe this issue came on gradually over time, not all at once.
The boat is an hour away, so I am sort of stockpiling ideas before I head down there. My plan is to put the winky-blinky on it, do a fuel pressure test and hopefully a vac test on the fuel lines. Also plan to test the 02 sensor and check the poppet valve.
History on the engine is as follows: supposedly professionally maintained till 2005, at which point I got a hold of it. I do fuel filters every year and generally kept up with the ringfree but didn't this year. New plugs towards the end of last year, the ones I took out were actually pretty clean.
I just got the yamaha service manual and realized I'm supposed to be checking and cleaning the 02 sensors - so I pulled that and took a look, it was actually quite clean. Never changed the low pressure fuel pumps. The only issue I have had with these engines was the screen on the high pressure fuel pumps, which appeared to get fouled due to some evil action of ethanol.
Anybody have any other thoughts on what I should be thinking? From reading this board and others I'm thinking low pressure fuel pumps or 02 sensor - I'm just a little unsure of those items because the engine runs fine once it is in gear and up to speed. I haven't checked for loss of rpm at WOT, but I'm not noticing any lack of power or surging at 4500 rpms (when the screen in the VST filter got clogged that was the main symptom) I would think a pinhole in a fuel line or bad pump would cause problems at higher RPM's, but the complexities of EFI sometimes confuse me.
When first starting from a cold start, I can start it, it idles OK for maybe a minute, then starts to cough and sneeze and stalls. Starting it after that results in pretty quick stalling.
I can't say for sure, but I believe this issue came on gradually over time, not all at once.
The boat is an hour away, so I am sort of stockpiling ideas before I head down there. My plan is to put the winky-blinky on it, do a fuel pressure test and hopefully a vac test on the fuel lines. Also plan to test the 02 sensor and check the poppet valve.
History on the engine is as follows: supposedly professionally maintained till 2005, at which point I got a hold of it. I do fuel filters every year and generally kept up with the ringfree but didn't this year. New plugs towards the end of last year, the ones I took out were actually pretty clean.
I just got the yamaha service manual and realized I'm supposed to be checking and cleaning the 02 sensors - so I pulled that and took a look, it was actually quite clean. Never changed the low pressure fuel pumps. The only issue I have had with these engines was the screen on the high pressure fuel pumps, which appeared to get fouled due to some evil action of ethanol.
Anybody have any other thoughts on what I should be thinking? From reading this board and others I'm thinking low pressure fuel pumps or 02 sensor - I'm just a little unsure of those items because the engine runs fine once it is in gear and up to speed. I haven't checked for loss of rpm at WOT, but I'm not noticing any lack of power or surging at 4500 rpms (when the screen in the VST filter got clogged that was the main symptom) I would think a pinhole in a fuel line or bad pump would cause problems at higher RPM's, but the complexities of EFI sometimes confuse me.