MerCarb adjusting after rebuild and question about base gasket

[Kubaat3lover]

Hello fellow boaters,
During the winter I have rebuilt my MerCarb because it was running quite richy and the choke was wrongly set and caused my problem which Ive discovered thanks to You guys.
Next question is regarding the adjustment, Do I really need vacuum gauge for that?
Ive got 4.3L Mercruiser from 2005.
Also the question is about the base gasket, originally it was TKS Carb but someone changed it to the MerCarb, Ive got extension sleeve under the carb so the question is do I need gasket with 1 hole or with 2 holes?

Thanks!

 

[Lou C]

If there is no place to hook up a vacuum gauge you can also use an accurate digital tach to set idle mixture.

 

[Kubaat3lover]

Ive bought digital IR tachometer for this

 

[Scott06]

My mercarb used the two hole gasket. You can tune it without a vacuum gauge. I usually start with the idle mix screw out about a turn and a half. Turn it in (lean) until it starts stumbling, then turn it out (rich) until it stumbles. Usually setting it between these is best idle setting.
once mix is set set the idle speed, best done in the water in forward, about 650 rpm.

 

[Kubaat3lover]

My mercarb used the two hole gasket. You can tune it without a vacuum gauge. I usually start with the idle mix screw out about a turn and a half. Turn it in (lean) until it starts stumbling, then turn it out (rich) until it stumbles. Usually setting it between these is best idle setting.
once mix is set set the idle speed, best done in the water in forward, about 650 rpm.

Do You have plastic base extension? According to my S/N engine I will need 1 hole gasket BUT its for TKS Carb... ive got MerCarb now...

 

[Fun Times]

Carburetor Kit for (TKS) looks like this...

While Carburetor for (Mercarb) = this set up, Carburetor and Throttle Linkage

4.3L CARB ALPHA/BRAVO - 0M615000 THRU 0W300012

4.3L CARB ALPHA/BRAVO - 0M615000 THRU 0W300012

www.mercruiserparts.com

 

[Kubaat3lover]

Carburetor Kit for (TKS) looks like this...

While Carburetor for (Mercarb) = this set up, Carburetor and Throttle Linkage

4.3L CARB ALPHA/BRAVO - 0M615000 THRU 0W300012

4.3L CARB ALPHA/BRAVO - 0M615000 THRU 0W300012

www.mercruiserparts.com

Thanks so for TKS its 2x 1 hole gasket ,
for MerCarb its 1x 1hole gasket + 1x2hole gasket,
but look here:

• 4.3L (GEN +) (2 BBL.) GM 262 V-6 1998 - 0L010044 THRU 0M614999 /

Carburetor And Throttle Linkage(2 Barrel)

Carburetor And Throttle Linkage(2 Barrel)

www.mercruiserparts.com

here we have 2x 2hole gasket ..
Whats the difference?? Why its different design

 

[Scott06]

I cant explain it but my 1990 3.0 with mercarb had a two hole gasket and no spacer... but there was one large hole in manifold. Both gaskets came in my rebuild kit i could not get it to idle correctly with the single hoke gasket. Two hole gasket worked fine. It made no sense to me but clearly there is some difference. If the drawing shows 22 hole gaskets with the Mercarb that is what I would use

 

[Fun Times]

It's been a awhile now but I believe it was because on some setups there was a engine running issue that arose as one of the fuel flow circuits became obstructed with the 2 hole cut out at the top so they opened the gasket up starting at the next set of serial numbers above the you mentioned...All of which may had something to do with what engine serial number the carb was on as there is a serial number change between carb part numbers as listed here in the two item number 9's located in the "Notes", https://www.mercruiserparts.com/bam/subassembly/31490/9021/70

4.3L (GEN +) (2 BBL.) GM 262 V-6 1998 - 0L010044 THRU 0M614999

vs, 4.3L CARB ALPHA/BRAVO - 0M615000 THRU 0W300012

With that all mentioned as more of an just in case you notice an odd engine running idle issue that you can't seem to "adjust" out with the mixture screw, you may be able to use the two cut out gaskets as they all show a 2 in the "Quantity Used" while the one open gasket shows 1 quantity used.

Where did your new to you carb come from, is there a year, an engine serial # or part number on it somewhere maybe?

 

[Kubaat3lover]

On my carb is stamped 807764N and below 18 6 04
engine S/N is 0W326935 but as I mentioned before it was TKS earlier now MerCarb

 

[Fun Times]

Running your 807764 number shows it ought to come with the 2 hole gasket, https://www.mercruiserparts.com/864941a01-carburetor

Looks like the main difference between the 2 are thickness. Gasket thickness: .060" is for the 1 hole and the 2 hole Gasket thickness is .030''.

Mercarb Marine Gaskets - Carburetor Parts & Kits for Carter, Ford Motorcraft, Holley & Rochester Carburetors

 

[Kubaat3lover]

2 hole gasket even with the plastic sleeve extension under the carb?

Thanks! Great info

 

[Fun Times]

That should work okay.

 

[Kubaat3lover]

Ok I will have a look later on April when the season starts... Ive noticed that 1 hole gasket is thicker than 2 hole...