2000 merc 150 efi/stumbles at off idle speed

[jnowicky]

Went back to Merc mechanic and after passing all computer tests he explained that now its "throwing parts at it". Well, the throttle position sensor was first, then plugs and tested on the dyno. Seemed OK. Took out today, same old problem. Starts easy, idles OK, Gets to 2000 RPM and then stumbles. When pulling the boat out after testing, had trouble driving it onto the trailer. Please help!<br />Thanks,<br />John

 

[JB]

Re: 2000 merc 150 efi/stumbles at off idle speed

Hi, John.<br /><br />As I understand it, late model Mercs cut off some cylinders at idle and don't pick them up until about 2,000rpm. That often makes the transition rough unless the throttle is at WOT.<br /><br />Some of the Merc experts here might have some advice on that, but it seems to me that if the Merc wrenches can't fix it it will be hard to do.<br /><br />Good luck.

 

[jnowicky]

Re: 2000 merc 150 efi/stumbles at off idle speed

the stumbling occurs from 2000 rpm up to WOT. The mechanic is ready to start throwing parts at the engine ie: stator, trigger, cdi and he even said it might be the computer. By the time he's through, I could probably buy a new engine????!!!<br />Interesting about the cutting out of cylinders at idle. Maybe the item that controls the other cylinders kicking in is the culptit.

 

[Reel Appeal]

Re: 2000 merc 150 efi/stumbles at off idle speed

jno,<br /> If your mechanic said that to you I would reccommend finding another mechanic.When a mechanic says something like that to me it's a red flag in my book "It might be the computer".Most parts can be tested for defectivness.Do not let him throw parts and time into it(and your money)if he cannot figure out what the problem is.The problem must be isolated(through testing) before any repairs are made.Did he test any of those components you mentioned?It also could be fuel related,such as clogged injectors or restriction somewhere else.Was the motor synchronized?(link and sync)<br /> This same scenario happened to me a few years back on an older Merc..My tech started throwing parts and time(stator/trigger,etc.)into it.I got it back w/same symptoms.After the $500+ bill ,I found dirt in the carbs .No more problems since.I found out later the mechanic quit or was let go about a month later.Just my experience.

 

[jnowicky]

Re: 2000 merc 150 efi/stumbles at off idle speed

Thanks for the info. I'll tell the mechanic to first test the components until the faulty one is found. This can get very expensive, especially since the warranty period is over.