Running rough when cold, helping to diagnose the problem with Mercarb

[Kubaat3lover]

Ive tried it and opened by hand and it wasnt any improvement at all.

 

[alldodge]

Ive tried it and opened by hand and it wasnt any improvement at all.

That is a new, so lets explore it more

Its my understanding that once warmed up the boat runs good. If that is the case does the exhaust smell rich?

If motor is shut down, how does it restart after a few seconds an after an hour or so?

 

[Kubaat3lover]

For the 1st start I give 1 full throttle then 1/4 of throttle, 1st start of the day ( cold , cold) it runs rough, little shakes like one of the cylinder doesnt work, i need to keep at least 900-1000rpms to run her smoother.
During this period smeell stinks and you can see a little smoke behind the boat.

I will try to make a video of the 1st start how does it look etc.

Its my understanding that once warmed up the boat runs good. If that is the case does the exhaust smell rich?

I will have to find it out, dont remember how it smelss when rich, I hope i will be able to tell You...

If motor is shut down, how does it restart after a few seconds an after an hour or so?

After a while When warm it runs great, after long or short run,whatever when switched off It starts after half turn of the starter, without priming etc... It runs nicely i would say

 

[alldodge]

After a while When warm it runs great, after long or short run,whatever when switched off It starts after half turn of the starter, without priming etc... It runs nicely i would say

Other then this comment I might think it may be flooding.

Once started when cold and the choke can be opened up means its getting more fuel then it can burn. When it warms up it burns fuel better so more is getting burned.

Pull some plugs and if they are black and maybe some soot then its running rich even after warming up. This would mean the carb needs a rebuild and adjusting. My guess would be the float level

 

[Kubaat3lover]

On my 2nd post ive uploaded pic of spark plug from cylinder no 3.
it fires also easy when cold, only this rough idle...

 

[alldodge]

Forgot, that doesn't look bad

Your still saying when cold the choke can be opened all the way and it doesn't change anything?

 

[Kubaat3lover]

That is correct... I’ll try again tomorrow open the choke by hand and see, maybe I’ll try not to pump the throttle before start ? Just try at idle??... but it’s carb!
btw. I’ve found pics of my spark plugs during replacement from the 2019 season, looks pretty richy right? But the latest are nice quite brownish/tan so I don’t know

 

[Kubaat3lover]

Well I think I need try To loose choke screws and make it leaner maybe then we will see...

 

[alldodge]

Agree, they do look like there running rich

You didn't happen to replace the fuel pump some time back?

 

[Kubaat3lover]

No never

 

[alldodge]

OK, was hoping maybe we had to much fuel pressure, so no go with that

 

[Kubaat3lover]

When starting her tommorow for a video, do I have to keep 1000rpms or let her rough at idle @ 600-800rpms to show that You on a video? Does it matter?
also pumping throttle or not if it helps for the investigation?

also I have got small screw with spring near the CAM it’s idle screw if you recall, do you know if this one regulates my idle @ gear?

 

[alldodge]

I want to know if it will stay running with the choke open. Will stay running at idle with choke closed but not open or if it doesn't matter

also I have got small screw with spring near the CAM it’s idle screw if you recall, do you know if this one regulates my idle @ gear?

Yes that should be the idle screw

 

[AShipShow]

Only a chance to keep it higher is to keep it on idle or when boating, the problem starts when I have to leave my dock/ marina in an idle fwd gear but on that settings ive got 650-800rpms and engine is running rough and you can smell smoke/fumes until warms up...which is quite not nice to the other boaters in my marina is that okay? Is it a problem with a choke? i still cannot move the screws, ill put some liquid wrench and try another day
when warm its fine.





What Do You mean? Ive got screw with a spring also on the CAM , right?

Mercarbs DO have a fast idle cam... As you said, your idle adjustment screw (screw with the spring) rides on the cam.. Its eccentric so as the choke closes, it opens the throttle more.

 

[Kubaat3lover]

Hi Mad, I have watched all your vids about Mercab and probably will use your help in carb rebuilt.
Anyway, today luckily ive removed all screws and set the choke.
I have tried to make as much videos as possible to make it clear for You guys so I will apprecaite your patient and help to have a look.

When setting a choke on Mercab Mikes Carb said in this ( https://www.youtube.com/watch?v=LN3qJrQS3Sg& )

video on 1:39 to set the full throttle,
I did mine with throttle @ idle, is that incorrect and I need to do this again?

1. How I set my Choke:

2. First start of the day, shaking explained, I didnt pumped full throttle before engine start, maybe thats why it didnt start from the 1st time? I never had this before, maybe becasue of Camera btw. today we had 86Fs (30*C) so maybe that wasnt the best weather to show this roughness, anyway You can see the general issue:

3. Here I have recorded starting up hot engine after short ride, throttle @ idle

4. I saw also a little gap in the choke, maybe because it was still warm and not full closed?

5. Also I have noticed that choke unloader doesnt work @ full throttle, when choke is closed + full throttle choke is still closed, doesnt open a little also i think that the part which hits the CAM is missing, Am I right?

6. After thrtottle pumping I have noticed a little fuel around the basket outside the carb...

7. Ive noticed that throttle rod is touching the accelerator fuel pump when on idle, switching from gears it "HITS" this rod.. you can Hear and see it on the videos, heres a pic

​

 

[alldodge]

Your correct the stud is causing an issue. The reason you don't need to move the throttle to set the choke is because the idle screw is not being used. Either the stud is resting against the linkage or the throttle plate will not let it fully close.

Need to cut the stud just past flush to let the lock nut hold, or get a different stud.

Might be able to just get a stainless bolt, and use lock nuts on the linkage side only



Fuel outside would mean the carb is leaking, and would cause it to run rich

 

[Kubaat3lover]

Your correct the stud is causing an issue. The reason you don't need to move the throttle to set the choke is because the idle screw is not being used. Either the stud is resting against the linkage or the throttle plate will not let it fully close.

Need to cut the stud just past flush to let the lock nut hold, or get a different stud.

Might be able to just get a stainless bolt, and use lock nuts on the linkage side only



Fuel outside would mean the carb is leaking, and would cause it to run rich

Thank You for your reply!
But I didn't get it , Does this blocked rod is causing the problem? I didnt get this:
"Need to cut the stud just past flush to let the lock nut hold, or get a different stud.

Might be able to just get a stainless bolt, and use lock nuts on the linkage side only"

What do You mean? To just cut the stud ? I was thinking about loosing the nuts and tryin' to move the stud away from the rod.
What could cause this interference??

Take care!

EDIT:#
Yes, the idle screw is not touching the CAM I have never touched it, it was from the beggining I got a boat.
When I Screw it 2 turns according to the manual it will block the choke lever/butterfly ( im not sure I explained it correctly)

 

[alldodge]

If you can loosen the rear nut and tighten the others then this would work. The issue is most carb studs are not threaded all the way from one side to another. So would just cut the end off the stud on the carb side

 

[Kubaat3lover]

And thats it? Do You think it will fix the problem with this cold starts??
Now I have leaned the choke, do I need to return to prevs settings?

Thanks!

 

[alldodge]

Actually, your motor starts easy even cold, its just the short time of rough running.

I think you need a carb rebuild to clear things up. Could fix it to where it would be smoother.

The warm restart I was wondering if it was harder after sitting for 1 or 2 hours. Seeing everything else the motor is running fairly well