1992 Merc 200 HP Fuel Problem??? UPDATED

[JohnnySCV]

Hi Folks! I posted a question a month or so ago about a rough idle. After some discussion I removed, actually just disconnected the idle staballizer, in an effort to get a smoother run at idle and low rpms. It seemed to help, but once I got the chance to test it, there was really no difference. The problem is the engine stalls at low RPM's and is a really pain to start, especially once it's been running and then left off for a while when fishing. The engine runs good once the RPMS get up there, but if I punch it coming out of the whole it does bog a bit sometimes. I have a service manual and have check idle, timing, compression, changed plugs, used carb cleaner, powertune, I've tried 87, 89 and 91 octane, run sea foam, changed fuel filter......

Specs on the engine: 1992 Mercury 200 HP 3.5 liter carb not EFI.

I am considering doing a carb rebuild, anyone else have any thoughts?

 

[BullyARed]

Re: 1992 Merc 200 HP Fuel Problem???

Re: 1992 Merc 200 HP Fuel Problem???

I would clean the carbs. I did that on my 2000 Mercury 200HP. It didn't take long (about 1hr at most for 3 carbs). If you clean the idle screws, make sure you count number of turns unless you know how to adjust the carb idle screws. I would then replace the fuel filter, the fuel/water separator (if you don't have one, strongly recommend it), and the primer bulb. This should solve/minimize the fuel problem. Give it a try and see how it goes.

 

[JohnnySCV]

Re: 1992 Merc 200 HP Fuel Problem??? UPDATED

Ok, I took the carbs off, took them apart, soaked them, rinsed and blew out all parts with a compressor, reassembled with new gaskets and reinstalled. Are parts were kept with the same carbs and all carbs were put back in the same spots. I was careful not to touch the two screws with white caps. Once installed I checked for leaks, squeezed my bulb until firm and started the boat. I fired up right away, however the idle is about 1200 RPM were previoulsy it was 725 or so. Any thoughts as too what changed my idle and what my next step should be?

 

[jmj120]

Re: 1992 Merc 200 HP Fuel Problem??? UPDATED

My guess, and it's just a guess, you might have fixed your problem. I'd idle it down a bit and take it to the lake. The two screws with the white caps are your fuel/air mixture screws. The service manual indicates they should be backed off 1.5 turns from lightly seated.
Has someone tinkered with these before you?

 

[JohnnySCV]

Re: 1992 Merc 200 HP Fuel Problem??? UPDATED

I have no idea if anyone has messed with the carbs. If they did it must have been years ago because the gasket that were on there OLD! I have had the boat about 9 months and have done a series of things to get in better shape, this being the most involved to this point. I will try backing down the idle and giving it a run. Idle should be about 700 RPM's correct?

 

[jmj120]

Re: 1992 Merc 200 HP Fuel Problem??? UPDATED

Mine was idling at 800.
Hopefully you solved your problems. Were the carbs dirty? I have mine pulled now, they were pretty bad, not terrible. Hope it solves my problem. Waiting on gaskets.

 

[JohnnySCV]

Re: 1992 Merc 200 HP Fuel Problem??? UPDATED

Mine was idling at 800.
Hopefully you solved your problems. Were the carbs dirty? I have mine pulled now, they were pretty bad, not terrible. Hope it solves my problem. Waiting on gaskets.

Carbs didn't seem too bad, I mean it's not like I found Hofa's body in there or anything. It seemed to me that carbs had a lot of residue on them. When I compared a cleaned carb to one of the dirty ones I was really suprised at the difference. After soaking some of the jest and clowing them out with the compressor it also appeared that the wholes were quite a bit bigger than when I started. Lets hope it works.

 

[jmj120]

Re: 1992 Merc 200 HP Fuel Problem??? UPDATED

I hope it works for you. You could see dirt particles in mine, and the gaskets were mushy. Looked like someone them apart and cleaned them and didn't bother with new gaskets.
Did you look at your reeds?

 

[BullyARed]

Re: 1992 Merc 200 HP Fuel Problem??? UPDATED

Spray the throttle with WD-40 and all the linkages outside the carbs cleaner and let it dry and then with WD-40. Make sure the linkages and chokes are moved and closed properly. If idle is still high, it may be the time to tinker with the idle screws. Make sure count them. Adjust three carbs "slowly 1/8 or 1/4 turn" until you get the right idle speed.