General carb questions

[dcf1999]

I’m rebuilding my carb for a 4.3 Mercruiser.

My first general question is that I notice a large hole that goes through the air horn and into float bowl area. (See red circles in pics). What is that for? It seems like a pretty good way to get contaminants into the carb if stuff can fall through there and into the area where the float, jets, and power valve are. I understand that the flame arrestor should prevent items from getting in there. Just never seen that before.

Second question… the rod with the spring that’s attached to the air horn (next to red circle on first pic). Does that need to come out when I clean it? It seems to move as it should, just didn’t know if gunk can get back into the base. If so, how do I remove it.

Thank you,

Dave

 

[Bondo]

I’m rebuilding my carb for a 4.3 Mercruiser.

Ayuh,...... Step #1 in rebuilding a carb, is complete disassembly,.....

 

[dcf1999]

Ayuh,...... Step #1 in rebuilding a carb, is complete disassembly,.....

Yes that’s obvious. I’ve rebuilt many carbs and never rebuilt a carb that isn’t completely disassembled.

This is the first time with this specific carb. It’s 100% disassembled right now (except for that pin).

If you’re referring to it not being “100% disassembled” because the power valve pin (or whatever it’s called) that I’m asking about, the shop manual doesn’t say to take that out nor does it give instructions on how to remove it. It doesn't appear to just pull out and I’m not going to force it if it’s pressed in or something. Thus the question.

Any idea about that hole in the air horn?

 

[dcf1999]

Oh, I remembered one last question. The shop manual (and Quicksilver rebuild instructions) and online parts diagram shows gaskets behind the 2 jets. When I pulled jets, I didn’t see any gaskets. I tried picking at the base where the jets screw into to see if they were stuck onto the metal, but it appears there isn’t any there. Anyone encounter this? Not sure if the rebuild kit includes gaskets for the jets, I’ll have to look.

In regards to that pin with the spring on it, from doing a little more research, it seems like it’s not a serviceable part (or something that should be removed). You can’t buy it separately.

So I guess my only 2 questions now is about that hole (more just for curiosity) and the gaskets for the 2 jets.

 

[Scott06]

I’m rebuilding my carb for a 4.3 Mercruiser.

My first general question is that I notice a large hole that goes through the air horn and into float bowl area. (See red circles in pics). What is that for? It seems like a pretty good way to get contaminants into the carb if stuff can fall through there and into the area where the float, jets, and power valve are. I understand that the flame arrestor should prevent items from getting in there. Just never seen that before.

Second question… the rod with the spring that’s attached to the air horn (next to red circle on first pic). Does that need to come out when I clean it? It seems to move as it should, just didn’t know if gunk can get back into the base. If so, how do I remove it.

Thank you,

Dave

The hole in the airhorn is the bowl vent. Where it vents is inside the flame arrestor so that keeps debris out.


the rod with the spring is the actuator for the power valve. engine vacuum will pull it up when at light throttle, when vacuum drops as throttle is opened, the spring pushes it down to richen the mixture. As long as it moves freely leave it alone as it is staked into the airhorn.

 

[Scott06]

Oh, I remembered one last question. The shop manual (and Quicksilver rebuild instructions) and online parts diagram shows gaskets behind the 2 jets. When I pulled jets, I didn’t see any gaskets. I tried picking at the base where the jets screw into to see if they were stuck onto the metal, but it appears there isn’t any there. Anyone encounter this? Not sure if the rebuild kit includes gaskets for the jets, I’ll have to look.

In regards to that pin with the spring on it, from doing a little more research, it seems like it’s not a serviceable part (or something that should be removed). You can’t buy it separately.

So I guess my only 2 questions now is about that hole (more just for curiosity) and the gaskets for the 2 jets.

The digram does show what look like metal sealing washers where the jets seat so I would get them this may not be for your exact engine but part 30 is a gasket kit looks like for whole carb.

https://www.marineengine.com/parts/mercruiser-sterndrive-parts/43l-gen-2-bbl-gm-262-v6-1998/0l010044-thru-0m614999/carburetor-mercarb-two-barrel

do yourself a favor and get a ultrasonic cleaner from harbor freight. Put carb cleaner in it and clean the carb parts when stripped down. It’s well worth the investment

 

[dcf1999]

The digram does show what look like metal sealing washers where the jets seat so I would get them this may not be for your exact engine but part 30 is a gasket kit looks like for whole carb.

https://www.marineengine.com/parts/mercruiser-sterndrive-parts/43l-gen-2-bbl-gm-262-v6-1998/0l010044-thru-0m614999/carburetor-mercarb-two-barrel

do yourself a favor and get a ultrasonic cleaner from harbor freight. Put carb cleaner in it and clean the carb parts when stripped down. It’s well worth the investment

Thank you! I already have a couple of nice ultrasonic cleaners. Different sizes for different carbs. This will require my larger one. I bought it a few years ago specifically for cleaning carbs and WOW… how nice they work. I always use them when doing a carb cleaning.

I will look closer for those washers and see if my rebuild kit includes them. If not, I’ll order them. I’m sure they are cheap.