2 brl to 4 brl conversion 4.3 vortec

gtfireftr

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New to forum, and I did a search and found little on the subject.
I have some issues with my 2 barrel Mercarbs.... I have twin 4.3's (190 hp), and the carbs seem to dump fuel once shut down.
When I start cold it is all loaded up, and takes a few minutes to clear out. Once it is clear she runs fine.... I am not happy with this, I am sure it
is not good for the engines. I am going to make a move on new carbs, but I was thinking for a few more bucks I could change intakes and get
new Edelbrock 1409 carbs.... Probably cost an additional $600 or so..... Which is okay with me, as long as the finished product is good.
I am not overly concerned with a power increase (but if it does that is great), I am more concerned with the engines running good.....
Any thoughts and advice is greatly appreciated.....
TIA
 

thumpar

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I am going to guess this is a big boat and not a speed boat. You would probably not notice any performance increase. I would just rebuild the carbs you have if that is really the problem. A rebuild kit will run you under $30.
 

gtfireftr

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I am going to guess this is a big boat and not a speed boat. You would probably not notice any performance increase. I would just rebuild the carbs you have if that is really the problem. A rebuild kit will run you under $30.
Yea she is a cruiser.....
 

gtfireftr

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Sea Ray 290 DA. I have rebuilt the carbs previously, not a fan at all of the Mercarbs.
If I can upgrade to new Edelbrock 1409's, and have her tun great I will do that. Plus the additional hp won't hurt.
 

thumpar

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How long ago did you rebuild the carbs? They should be good for many many years. There may be a problem other than the carbs going on. You could try running off an external tank to isolate it some.
 

gtfireftr

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Rebuilt last year.
Pretty sure it's a carb issue. 2 similar issues, but different as well. !!!! Lol.
My question is will the 4 barrel carb create an issue of bogging or anything else??
I know that they had an option of the 4v, so I think it should be okay. I was curious if anyone has any real world experience doing this swap?
 

thumpar

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The 4bbl will work but you have something else going on. Carbs last for years. Figure out what is the problem before just throwing parts at it.
 

gtfireftr

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The carbs have never been 100%.
Always an issue loading up. Port had a flat spot. Etc.
 

Rick Stephens

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I really like the 1409 sitting on a Performa intake. I have a lot smaller boat and just one of em, but it was an easy fit and the 1409 is nice to work on.

You don't say what year your boat is. If it is a Vortec, don't purchase the calibration kit for 4.3L V6. My opinion is the kit is for pre-Vortec and will run WAY too lean. Couple of us have come to the same conclusion on calibrating and have exactly the same starting place for jetting. Is a lot better place to start for the Vortec. If you do go that way, check out this thread.
http://forums.iboats.com/forum/engi...ves/10154544-stumbling-edelbrock-1409-4-3l-v6

Rick
 

jimmbo

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The 4.3 is not a big engine and unless the current Rochester(mercarb) is under sized by a considerable margin changing to a 4bbl is not going to give any noticeable increase in power.

"Port had a flat spot" ????

"Loading up", Float set too high.

You have it set in your mind you 'need/want' a 4bbl carb and will rationalize till you have it

A marine version of a Q-jet, or Holley Spreadbore, both of which have small primaries, may be a better choice for a small engine
 
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thumpar

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The 4.3 is not a big engine and unless the current Rochester(mercarb) is under sized by a considerable margin changing to a 4bbl is not going to give any noticeable increase in power.

"Port had a flat spot" ????

"Loading up", Float set too high.

You have it set in your mind you 'need/want' a 4bbl carb and will rationalize till you have it

A marine version of a Q-jet, or Holley Spreadbore, both of which have small primaries, may be a better choice for a small engine

I agree with that. You need to figure out what is going on before throwing parts at it.
 

gtfireftr

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I really like the 1409 sitting on a Performa intake. I have a lot smaller boat and just one of em, but it was an easy fit and the 1409 is nice to work on.

You don't say what year your boat is. If it is a Vortec, don't purchase the calibration kit for 4.3L V6. My opinion is the kit is for pre-Vortec and will run WAY too lean. Couple of us have come to the same conclusion on calibrating and have exactly the same starting place for jetting. Is a lot better place to start for the Vortec. If you do go that way, check out this thread.
http://forums.iboats.com/forum/engi...ves/10154544-stumbling-edelbrock-1409-4-3l-v6

Rick
So did you end up with the pretty much out of the box 1409? I do have a vortec 4.3 (1998)....
I read the thread, and saw what you installed, but I am not sure how that compares to the stock 1409..... How difficult is it to change jets, metering rods, etc...
I assume you need to take the top off of the carb to do this...
Thanks for the replies as well.....
 

jimmbo

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Did you ever check to see if the choke pull offs were functioning and/or set correctly?

Swapping intakes and carbs isn't rocket science, however you need more than a basic understanding of carburetor theory to make the correct changes for proper calibration once it is installed
 

Maclin

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Not sure on the Mercarbs, but some carb designs have welch plugs in the bottom of the fuel bowl(s). Those need to be re-epoxied occasionally. The fuel just drips/runs out into the intake plenum until the bowl drains. Residual pressure in the fuel line between the fuel pump and the carb can keep the bowl full and the drip/run going for a while after shutdown.
 

Rick Stephens

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So did you end up with the pretty much out of the box 1409? I do have a vortec 4.3 (1998)....
I read the thread, and saw what you installed, but I am not sure how that compares to the stock 1409..... How difficult is it to change jets, metering rods, etc...
I assume you need to take the top off of the carb to do this...
Thanks for the replies as well.....

Correct jetting (for me) was midway between stock out of the box and the 1485 kit. Stock the main jets are .098, I used .095, the 1485 kit is .089. Takes about 15 minutes total each time you need to swap out a main jet as you do have to pop the top on the carb. Takes about 5 minutes to swap out the metering rods as they can be done without popping the top. There are videos on the Edelbrock site showing this process from start to finish. It works exactly like they show.
 
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