Upgrade Carb from 2 barrel to 4 barrel

[brodie123]

I have an inboard Mercruiser inline 6 165hp with a 2 barrel rochester.

The intake manifold is the size for a 4 barrel and there is a reduction plate to make the 2 barrel fit.

I got ahold of a 4 barrel Holley that I'd like to see if I can get to run on it.

I made an adapter to turn the 4 barrel around so the linkage is on the right side.

I have not been able to get it to idle.

I pump the gas a little and she revs way up and then immediatly dies off.

If I try to start it without giving it a little extra initial fuel, it doesn't turn over.


So my question is will the inline 6 not handle a 4 barrel or am I looking at a faulty carb?

 

[Bt Doctur]

Re: Upgrade Carb from 2 barrel to 4 barrel

Edelbrock 4bbl on mine , flawless

 

[CharlieB]

Re: Upgrade Carb from 2 barrel to 4 barrel

Hopefully that is a "Marine" carb and not just another automotive carb you are hoping to make work.


Marine carbs are designed to prevent any carb flooding from escaping to the engine bay, possibly creating an explosive atmosphere.

Second major difference is power valve opening point, autos have far more intake vacuum than any marine engine.

Check the postings at the top of this forum, Don has posted links to most all of the factor service manuals, you can find Merc's proceedures for servicing the original model 4 barrel carb. That should guide you thru installation and adjustment.

Edelbrock does handle a Marine version of the Q-jet, find the right size (small CFM) and it should perform well.

 

[brodie123]

Re: Upgrade Carb from 2 barrel to 4 barrel

Thanks. It is a marine carb but I'm thinking may be designed to handle more cfm than my inline 6 asks for at idle?

I do have the manual and used it for the setup - will go through it again.

So technically she should be able to idle as long as the carb is working properly & no gasket leaks?

 

[mkast]

Re: Upgrade Carb from 2 barrel to 4 barrel

What size is the four barrel?
What's the list number on the air horn?

 

[brodie123]

Re: Upgrade Carb from 2 barrel to 4 barrel

I'm not sure but here's the #'s off of it.

rochester quadrajet 17059286
2046

Any good places to look up the CFM for it? I'd like to compare the old carb as well (Rochester 2 barrel).

Thanks!

 

[brodie123]

Re: Upgrade Carb from 2 barrel to 4 barrel

was that the right info I gave you? It was on the side of the carb.

 

[Just Add Water]

Re: Upgrade Carb from 2 barrel to 4 barrel

I got ahold of a 4 barrel Holley that I'd like to see if I can get to run on it.

What size is the four barrel?
What's the list number on the air horn?

I'm not sure but here's the #'s off of it.

rochester quadrajet 17059286
2046

Any good places to look up the CFM for it? I'd like to compare the old carb as well (Rochester 2 barrel).

Thanks!

So which is it?? A holley, or quadrajet?
Begs the question if it's really a marine carb again doesn't it...??

 

[brodie123]

Re: Upgrade Carb from 2 barrel to 4 barrel

yup sorry - should not have said Holley. It's a Rochester and came off a boat - I have no idea what size engine.

 

[brodie123]

Re: Upgrade Carb from 2 barrel to 4 barrel

Turned out to be a vaccuum leak - running great! Thanks!