2005 200hp Mercury carbuerator problem

[trunctj]

I purchased used, a Saltwater Edition 200 hp Mercury. Last of the carbuerator models. It starts right up, idles great, runs smooth at high rpms, good fuel economy. My problem is that when accelerating gradually, at 1800 rpms the motor bogs down and, if the throttle is not advanced quickly, stalls. The engine can be made to accelerate through this problem transition by engaging the fuel enricher (pushing in the key). The problem is not remedied by squeezing the fuel bulb. The problem does not occur when the engine is cold. I operate the boat at sea level, so I assume elevation is not the culprit.

I have cleaned the three carbuerators (the jets, and the ports) twice. No improvement. (I have not replaced any jets.)

Seems to me like the engine is running too lean during the mid range transition. I read that these carb's have vacuum ports for the mid range operation (not jets), which are intended to lean out the fuel mixture as the throttle is advanced through the mid range.

Anyone else experience this? Any ideas?

Are there replacement jets which would allow me to richen the mixture? Seems like a reasonable next step.

 

[jerryjerry05]

Re: 2005 200hp Mercury carbuerator problem

Fuel pump diaphram.Ethanol is messing with lots of things on outboard motors.
It's eating the inside of the hoses and weaking the diaphram.
Check for water in the filters.
You might have to replace all the hoses,squeezie too.J

 

[Faztbullet]

Re: 2005 200hp Mercury carbuerator problem

Are you sure you have jets in correct location as the jets are staggered on the WMV series carbs. If it only does it after its hot it and you have to it choke it to correct it ,its lean for some reason. Check your mounting gaskets and thermal air valve on cylinder head...

 

[trunctj]

Re: 2005 200hp Mercury carbuerator problem

One step forward, two steps back?
I don't think the mid range stalling is a jet problem. When I cleaned the carbs, the jets were significantly different, and couldn't be mis placed. I did visibly inspect the fuel pump diaphram (held it up to the sun and did not see any pin holes, nor was the membrane stiff). I'm not ruling the fuel pump out as the problem, but thought I'd go in a different direction before rebuilding it. And, I thought I had an easy fix. I adjusted the idle jets a bit to richen the fuel mixture. Yes, I know this only affects the idle mixture, however it seemed to help as I didn't get the "bogging down" in the mid range transition (@ 1800 rpms). Yea! I reasoned that having a too rich a mixture at idle might provide more fuel going into the mid range transition. However, after being on the water for a while, I found that the idle speed became too slow (surprise, surprise). So, I advanced the idle speed with the adjustment screw. Now it was difficult to hold a consistent idle and then the 1800 transition problem was back, and it was worse than ever. It was getting late, and time to get off the water....

Tomorrow's another day. I'll put the idle mixture back to where it was, re-adjust idle speed, and then check the thermal air valve. Something is failing sporadically, or the problem adjustment is just on the cusp of providing acceptable/unacceptable performance.

 

[jeffersondodson561]

Re: 2005 200hp Mercury carbuerator problem

How long has this unit been sitting, you didn't happen to buy from Bass Pro Shops did you. I have seen problems with them not properly treating sitting boats. Whats the S/N?

 

[backyard mechanic]

Re: 2005 200hp Mercury carbuerator problem

I would go to the manual and do a link and sync- carbs to the timing just to assure that is right. If that doesn't fix it, I'd bet the issue is float settings. Sounds as if the fuel is not being burned at the appropriate rate when cold therefore the enrichment valve is providing enough fuel supply. However ONLY when cold, meaning there could be a spark timing to carburetor linkage issue. I suppose an adjustment of the idle jets MAY do it but you're going to run rich when warm. That's no good either.

If it doesn't do this when the engine is warm the problem doesn't sound like carbs/fuel per se'. It may have to do with float levels but I'm going with a link and sync to fix the issue.

That's my two cents on the matter....

 

[CharlieB]

Re: 2005 200hp Mercury carbuerator problem

Carb float level is critical to smooth running at all throttle positions as well is the correct 'link and synch' of carb opening to ignition timing.

Idle mixture also is of major importance as to lean will cause hesitation or bogging both during throttle opening and/or at the transistion point in throttle from the idle circuit to the main jet. Too rich on the idle circuit will shorten spark plug life and cause rough running when idling for long.

The fact that squeezing the primer makes no difference indicates that fuel supply from the pump is adequate.

I suggest you verify the correct float settings iin the carbs, followed by following the OEM service manual to link and synch the carbs to the ignition timing. Then an on-the-water idle mixture adjustment, again per the service manual, to 'best' idle speed while IN gear, plus an addition 1/8 turn out (richer) to provide the additional fuel for acceleration. (Says the manual).

Test acceleration by rapid throttle opening to WOT, ANY hesitation then richen the idle mixture an additional turn out just the width of the screwdriver blade slot and retest acceleration. Repeat to perfection.

 

[trunctj]

Re: 2005 200hp Mercury carbuerator problem

Guys,
Thanks for the comments. I re-sync'd the carbs, but by and large, I think they were ok. I did richen the idle adjustment a total of about an 1/8 of a turn on all (6) screws, and found that this did the trick. I think that the transition through mid range, was so sensitive that it needed a little richer idle mixture to get through it without hesitating. Previously, I was probably running a little lean, without any noticeable issue. I hadn't tried adjusting this earlier, as it states explicitly in my manual that these jets affect only idle mixture. Live and learn.

Appreciate you guys helping out.