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

[Kubaat3lover]

Thank You, I was wondering about Carb Rebuilt with parts from Mikes Carburetor,
But really when the days are colder it runs worse than that, I ll try to make a video some day.

Regarding Idle Screw, the idle screw doesn't touch the CAM I, it was from the beginning I own a boat.
When I Screw it 2 turns according to the manual it it won’t allow the choke plate to move at all, is that correct?

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

No issues after sitting for 1/2hours

 

[alldodge]

Regarding Idle Screw, the idle screw doesn't touch the CAM I, it was from the beginning I own a boat.
When I Screw it 2 turns according to the manual it it won’t allow the choke plate to move at all, is that correct?

Yes that is correct. Normally the idle screw needs to be turned in to increase the idle just to keep it running. Yours idles fine without it touching so for me I think there is a problem

 

[Kubaat3lover]

Ok Looks we have a new problem Now, How to fix it Can You Help me?
cheers

 

[alldodge]

If it was mine I would pull the carb and do a rebuild. After taking it apart, check that the throttle places completely close, the body and base are flat and gaskets seal all surfaces. All channels are clean and accelerator, float and linkages are adjusted as specified

 

[Kubaat3lover]

will do That during the winter, im not from US so Thats Why I have to order it online, do you think MikesCarbPart rebuilt kit is fine?

on video #5 i don’t have a tang which you can bend to adjust the choke unloaded, it’s just missing. Why??!
ive found 2 topics on the forum about that but there wasn’t enough information why some of the carbs doesn’t have this feature?

jk

 

[alldodge]

Don't know if Mike's parts is correct. Look on the carb for a number, the number tells you what the carb is and what rebuild kit is needed

 

[Kubaat3lover]

its stated 807764N on the Carb, it looks like Mercarb, but originally I had TKS on my boat, someone just replaced it.
Do You know if I need base gasket with 2 holes or just 1 big ?

Take care,

 

[alldodge]

Don't know, can try to look it up if I knew the serial number

 

[Kubaat3lover]

Hello again,
so I’ve cut the stud so it’s no longer touching the rod.
I have adjusted idle cam screw according to manual, but when I screw it 2 full turns it hold my choke open, I cannot close it manually. With this setting my rpms are fine on idle when warm..

 

[alldodge]

Its ok that the choke won't close with the idle screw resting against the cam. This is why the throttle is pumped first on cold days to release the pressure from the cam so the choke can close when its cold.

The amount of turns is just the initial setting, its then adjusted to get the idle correct

 

[Kubaat3lover]

Oh thanks !
ok so with this cut stud the throttle is closing now all the way! hope that helps and I’ll do rebuilt this winter

 

[Kubaat3lover]

Hi i cannot edit my post, so on MadProps video

here at 10:42 he screws in the idle screw and then he closes choke, its very smooth and closing very easy,
but in my case i almost cannot move anything at all if i screw this screw in 2 turns

Ive found few topics about the issue but I dont get the answers...

https://forums.iboats.com/forum/engi...rb-help-please

https://forums.iboats.com/forum/engi...ercruiser-3-0l

Thanks

edit;
Because a picture is worth a thousand words Ive made a video regardinig the issue

 

[Kubaat3lover]

Sorry cannot edit my previous post:

Its ok that the choke won't close with the idle screw resting against the cam. This is why the throttle is pumped first on cold days to release the pressure from the cam so the choke can close when its cold.

The amount of turns is just the initial setting, its then adjusted to get the idle correct

so the choke is not always closed when cold then opening during thermostat warming up?

jakub

 

[alldodge]

so the choke is not always closed when cold then opening during thermostat warming up?

Yes, the idle screw will keep the choke spring (on other side of carb) will be trying to close the plate but the idle screw friction stops it.

The Mad prop setup is only for initial settings

Your choke plate and the cam rod should move independently from one another. You should always be able to close the choke plate by pressing on it, even when motor is warmed up. The 2 items on your carb are bound together and need to be freed up

 

[Kubaat3lover]

Ok ive got it, heres a video how it works when IDLE Cam screw is not screwed in, it moves freerly

but when I screw in this screw it will be a friction which keeps the cam from moving, i still dont know wheres the problem?
on the picture Ive marked place where is the contact between screw and cam and friction...

 

[alldodge]

My mis-speak, the choke can not be closed once open, this is do to friction. Now it probably can be closed if push hard enough.

The screw should be in, and it shows everything is working as it should, other then the idle screw can be backed all the way out and it still idles fine. At this point it should die

 

[Kubaat3lover]

So when choke opens when the thermostat will be warm how it close?
and Yes it dies when not screwed in now

 

[alldodge]

Yes it dies when not screwed in

Don't know what to say. The thread started and there was a pic and vid showing it wasn't touching and it was still idling. Now it will die

So guess in that case its all fixed

 

[Kubaat3lover]

Yes, looks like the problem was with this stud blocking the rod / throttle in open position.

And alldodge please tell me, choke opens when the thermostat will be warm but how it close when its blocked by this screw?

 

[alldodge]

The choke pot spring is what causes the choke plate to close. When motor is cold the spring applies more pressure to close the choke plate. The reason it doesn't close just sitting is because the friction on the idle screw against the cam.

The normal process to start a cold motor is as you have been doing, pump the throttle. When the throttle gets pumped the choke pot spring closes the plate. When the throttle comes back to idle it rest against the cam but the plate is already closed.

As the motor warms up, the spring releases pressure slowly, and in doing so the plate slowly opens up. When throttle is used again, the cam drops back down and now the plate cannot close at idle