1992 5.7 merc running too rich for too long at start up-gctid398234

[Guest]

Hello all, my 5.7 Mercruiser seems to be running too rich for too long at start up. It takes about 15min before the black smoke clears. If I engage the gear before it clears she stalls and it takes a while to start it up again, I presume its flooded with fuel. The temp comes up as normal. When started and fully warmed up it starts up fine for the rest of the day even being left fot three hours or so.

Any ideas guys?

Thanks

Mike

[yachtman]

Check to make sure the flame arrestor is clean. Beyond that it sounds like a carb rebuild is at hand.

[2850Bounty]

If this is a conventional carburetor with a choke chimney and choke plate, try re-adjusting the helix tension on the choke plate while the engine is stone cold.

Make sure that the heating element is working well, and make sure that as it warms the helix, the helix linkage is pulling the plate open.

.

[Guest]

Thanks Dave, the arrestor looks fine but will double check, hope its not a rebuild.

Gotta have a good look again Rick as Im not familliar with the workings of the carb. I presume the heating element is immersed in the water jacket of the engine (which works like the thermostat in the cooling system) then linked mechanically to the helix. Would I be reasonably correct in this assumption or am i way off once again

[2850Bounty]

Mike, I don't know when Merc went to their own carburetor for this engine.

Like said, if this is a conventional carburetor, the choke plate will be pulled OFF via a helix that is electrically heated.

An engine model number, or perhaps a photo or two would help.

[yachtman]

Rick may be right about the choke. I was tired when I posted and wasnt thinking the whole thing through.

[Guest]

Thanks guys, I know the info is sketchy, must row out and bring it in to dock off a swing mooring, put her out five weeks ago and havent seen a fine day yet so Im not missing any boating. Hope to get a good day this week , take a few pics and post them up, i know the engine and outdrive numbers are on a sticker on the carb cover.

I do suspect its a choke issue also as this rich running only occurs from a first start of the day then starts and runs fine for the remainder.

Thanks again

Rgds

Mike

from rain soaked Ireland, no wonder the place is so green:livid:

[Guest]

Heres a few pics of my carb, cant seem to see any electrical connections to the choke but appers that when the helix expands the link rod seems to be rubbing off the plastic cover, hadnt time to look at it closer as I had my two little daughters with me on the day.

Attached files [img]/media/kunena/attachments/vb/706012=29948-IMAG0512.jpg[/img] [img]/media/kunena/attachments/vb/706012=29949-IMAG0513.jpg[/img] [img]/media/kunena/attachments/vb/706012=29950-IMAG0514.jpg[/img] [img]/media/kunena/attachments/vb/706012=29947-IMAG0515.jpg[/img]

[2850Bounty]

That appears to be a Rochester Quadrajet carburetor with what some refer to as a "divorced" choke.



The Helix is actually picking up heat directly and mechanically from the exhaust cross-over within the intake manifold.

I'm going to suggest that the Helix is shot from 'ole Father Time, and needs to be replaced and re-adjusted.

Your engine serial number should get you to Merc's parts break down.

Or..... you contact a good Rochester source, and see if there is a conversion kit to bring this to a Helix affair that uses the electric heating element, and then abandon the OEM system........ but I don't know if such a thing exists.

.

[Vic_Stewart]

Take it to a carb repair facility and not to "Joe's Place" under the big oak tree. A real rebuld shop can clean and replace pieces parts that are not included in the typical off the shelf kit. Once done, all you will have to do is adjust the idle.

Vic

Ft Myers

[iceclimber]

Vic Stewart wrote:
Take it to a carb repair facility and not to "Joe's Place" under the big oak tree. A real rebuld shop can clean and replace pieces parts that are not included in the typical off the shelf kit. Once done, all you will have to do is adjust the idle.

Vic

Ft Myers

+1. Sometimes the shops have a rebuild sitting on the shelf and will swap you.