2000 mercury 200efi help!!!!!!!

buddyrohl

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Joined
Nov 29, 2011
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10
I have a 2000 MERCURY 200EFI. I had a new powerhead put in last summer and it's been a piece of junk ever since. The mechanic over oiled the fuel tanks for the brake-in period and plugs would foul every 5 min of run time. After finally getting past the break-in period the engine would run great at full throttle. It did however bog down and take awhile to get on plane. Then after stopping and starting a few times, I would start the engine and it would idle then put it in gear it would die and not start again. I would swap sparkplugs the first few times it did this and it would go again. The last time it did this the plugs didn't work, then I notice I couldn't get he bulb to prime. After getting towed in and getting home 2hours later I primed the bulb and it firmed up and the engine fired right up. Any thoughts on what might be the problem with this moneypit of mine would be appreciated. Can't trust the mechanic I took it to, so would like a few ideas before I take it to someone else.... THANKS.
 

Faztbullet

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Mar 2, 2008
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15,589
Re: 2000 mercury 200efi help!!!!!!!

Several things, not a 200 block, injectors flooding, ignition/sync/link problems, ECU or TPS problem. Better to take it to someone who can check it all.
 

H20Rat

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Mar 8, 2009
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5,199
Re: 2000 mercury 200efi help!!!!!!!

The mechanic over oiled the fuel tanks for the brake-in period and plugs would foul every 5 min of run time.

Although I admit I don't know much about merc EFI systems, I have lots of experience with EFI on snowmobile engines. Rule #1 is NEVER run oil through the fuel tank of an EFI system, at least not if you want your injectors to work right again... Again, merc might be different, so just a suggestion.
 

wired247

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Oct 8, 2011
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Re: 2000 mercury 200efi help!!!!!!!

Rule #2 is don't listen to rule #1.

Of course oil and fuel run through the injector. Its not a DPI motor. Mercury Laser EFI's ( what he has ) run the mixed oil and gas through the injectors. Its common for break in gas to go as heavy as 25:1 oil mix. If you are using the oiler you may have oil mixed in the tank. If you arent using the oiler the oil mixes in the tank. Once you get up and running the plugs should burn the extra oil off.

I think faztbullet might be onto something. Could be a 150 powerhead running a 200 ECU. $20 for a gasket to pull a head and find out. It would run way too rich and foul the plugs quickly. Or you could have a flooding injector, bad sensors, bad fuel lift pump etc.
 
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buddyrohl

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Nov 29, 2011
Messages
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Re: 2000 mercury 200efi help!!!!!!!

Thanks for the input. Anybody know a good mercury mechanic in southern indiana or northern kentucky? So far have had no luck anywhere I go....
 

wired247

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Re: 2000 mercury 200efi help!!!!!!!

What is the serial number located on the welch plug located on the top rear right (starboard) side of the powerhead?
 

buddyrohl

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Nov 29, 2011
Messages
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Re: 2000 mercury 200efi help!!!!!!!

The welch plug doesn't have any numbers on it. The only numbers I could find on the powerhead was 0072 if that helps or means anything. Thanks
 

wired247

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Oct 8, 2011
Messages
1,557
Re: 2000 mercury 200efi help!!!!!!!

You may have a replacement block. When you say you bought a "new " powerhead did you actually mean a NEW powerhead?
 

wired247

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Messages
1,557
Re: 2000 mercury 200efi help!!!!!!!

Might want to pull a head. Take a pic of the cylinder and post it here.
 
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