200 Mercury EFI does not idle

[detoolman]

Currently I have to rev the engine in order to keep it running. After 30 minutes or so of reving and extra throttle I can put keep the boat idling, but it idles at close to 2000. Can anyone give me a clue where to start? I was thinking it is possibly lossy fuel lines that suck to much air on idle but will pull more fuel when the throttle is engaged. But that is a very ignorant guess.

1994 Mercury 200 EFI
Serial No. OD285460

 

[Faztbullet]

Re: 200 Mercury EFI does not idle

Did it just start this or did you buy it this way????

 

[r.j.dawg]

Re: 200 Mercury EFI does not idle

Without a scan tool it would be guessing, but my guess would be the IAC valve needs replacing.

 

[ufm82]

Re: 200 Mercury EFI does not idle

#1- you're backwards. The fuel lines, if drawing air, would cause more issues at higher rpms. Idle would be OK but you would see issues under higher fuel requirement conditions. High idle on efi engines denotes excessive air but it is usually in the intake system. As mentioned above the IAC may be the culprit. Too much air results in a lean condition and the fuel system compensates, thus the high idle.

 

[Faztbullet]

Re: 200 Mercury EFI does not idle

This engine does not have a IAC.....

 

[r.j.dawg]

Re: 200 Mercury EFI does not idle

Hmmm. I just did a parts search and the serial number came back as a 225 Carb model.

 

[detoolman]

Re: 200 Mercury EFI does not idle

Unfortunately, I bought it this way.
This model is actually a 1994 Mercury 200 XRI, which is indeed Fuel Injected, not Carb. The XRI is the same as EFI which I thought would be less confusing.

 

[r.j.dawg]

Re: 200 Mercury EFI does not idle

Are you sure about the serial number.

 

[detoolman]

Re: 200 Mercury EFI does not idle

Yes sir.

 

[Faztbullet]

Re: 200 Mercury EFI does not idle

Serial# come backs as a 150/175/200 Xri series. Check the TPS sensor and fuel pressure first. It will not idle if fuel pressure is low....

 

[r.j.dawg]

Re: 200 Mercury EFI does not idle

I did find the correct info on the Merc site. The first site was the wrong info. Should have known better.

 

[detoolman]

Re: 200 Mercury EFI does not idle

I did a compression check:
1, 3, 5 - 100,110,115
2, 4, 6 - 125, 128, 125

I also did a wet test on 3 and the psi went up to ~120.
I am thinking this is causing the rough idle and I am guessing it is a piston ring. At this point I don't know if it is worth fixing. Someone mentioned that this model may not require the case to be cracked to remove the pistons. Does anyone know if this is true?

 

[1nebel0]

Re: 200 Mercury EFI does not idle

Hey, there is nothing wrong with your numbers...Sea Foam the motor and all will most likely get more even.....you need to check the tps voltage that requires a special $65 harness to hook up to your meter...Fuel pump pressure needs to be verfied or you are wasting your time as the injectors will not fire correctly...you should probably take it to a shop....

 

[detoolman]

Re: 200 Mercury EFI does not idle

Why do you think nothing is wrong with the compression numbers? I realize that not everyone agrees on acceptable cylinder to cylinder compression differences, but 100-125 seems unacceptable. Also, what benefit is seafoam really going to provide on a 2-stroke fuel injected motor?

 

[1nebel0]

Re: 200 Mercury EFI does not idle

While you number varience is greater than it should be, Sea Foam will level all your numbers out.. I Sea Foam every motor I buy, and own both when first acquired and on a yearly basis due to carbon from oil/gas mixture. I also Sea Foam all of my gas cars but that is another story...there is a post on this board explaining what to do with a EFI motor.. simply use a remote tank..can't remember the gas/sea foam ratio but it is a rich mixture of Sea Foam.. The motor will smoke like crazy..Also once warmed, pull out the plugs and load up the cylinders with Sea Foam and let it sit for a while..Again start it and watch the smoke....I promise you the numbers will change..please search for the post in regards to gas/sea foam ratio and also post your results....

 

[detoolman]

Re: 200 Mercury EFI does not idle

Thanks for the advice. My two cents is that it will help clean up gum in the fuel injector, but as far as the cylinders on a two stroke, it won't do much if anything. I think it helps clean cylinder valves on a 4 stroke but on a 2 stroke I haven't seen many reed valves with crystalization. Trust me, I want to believe sea foam will fix it and I am willing to try.

 

[1nebel0]

Re: 200 Mercury EFI does not idle

Not to bust your chops but we are not talking about reeds...piston rings get carboned up and the Sea Foam breaks down the carbon to free the ring, net result is better sealing....Injectors should be sent to Brucato who does all of my F.I. motors...look them up on the net...until you try the Sea Foam, Yamaha ring free, OMC carbon product or Merc's carbon product you are wasting time.....

 

[detoolman]

Re: 200 Mercury EFI does not idle

By all means, bust my chops. I posted to this forum because I am not an expert and wanted to learn something so I am grateful for the advice. I will add some sea foam and let you know how it turns out.

 

[jeffersondodson561]

Re: 200 Mercury EFI does not idle

I did a compression check:
1, 3, 5 - 100,110,115
2, 4, 6 - 125, 128, 125

Without knowing the history of this engine it is hard to say. From the compression results it looks like the engine has been rebuilt and bored over .030" on the port side (which would not be good for the fuel injection). I doubt any decarb would balance out the cylinders 25lbs. But a decarb might balance out the starboard side better.

 

[1nebel0]

Re: 200 Mercury EFI does not idle

Agreed...latest 115 in line 6 motor have 165lbs give or take in all cylinders...I Sea Foamed the hell out of it and they came down to 125...never seen anything that drastic happen but it did..this was a stock motor(1983) that must have never had anything done to it...I have done many motors and seen drastic results and then some with almost no results..kind of a starting point when I buy a motor or boat..