4.3 Carb vs 5.7 Carb

[Lukey220]

Hey everyone, I successfully swapped the 5.7 into my boat and only thing left is the carb… I cant find any specs on the carb I have only possibly due to its age. Curious on if the carbs would be similar between a 1981 Merc. 5.7 and 1988 merc. 4.3 other than the 4.3 being 2 barrel and 5.7 being 4 barrel. I don’t really know much at all about large carbs so any help would be appreciated. Would the 4.3 carb work or should I start looking for a 5.7 carb?

Thanks!

 

[Scott06]

Hey everyone, I successfully swapped the 5.7 into my boat and only thing left is the carb… I cant find any specs on the carb I have only possibly due to its age. Curious on if the carbs would be similar between a 5.7 and 4.3 other than the 4.3 being 2 barrel and 5.7 being 4 barrel. Would the 4.3 carb work or should I start looking for a 5.7 carb?

Thanks!

In a word no they are not the same carbs. Even if they were both 2 bbl carbs they would have different jetting and possibly the venturi cluster is different.

I went through the same exercise when I did a 4.3=>5.0 swap and got a Edlebrock 1409 and it works great, would recommend you do the same, should work pretty well on a 5.7 right out of the box

 

[Lukey220]

I

In a word no they are not the same carbs. Even if they were both 2 bbl carbs they would have different jetting and possibly the venturi cluster is different.

I went through the same exercise when I did a 4.3=>5.0 swap and got a Edlebrock 1409 and it works great, would recommend you do the same, should work pretty well on a 5.7 right out of the box

Awesome, thanks for the quick reply. Will start shopping around.

 

[Lou C]

Even if the carbs were identical; if they came from different displacement engines the jetting, metering rods; and various other parts will be different to allow for the greater volume of air flowed by a larger displacement engine.

 

[Scott06]

Summit Racing has them (1409) in stock.

Mecruiser part number 805359T throttle bracket will work with the 1409 as the 2 bbl carb bracket will not. Makes a nice clean install of throttle bracket

 

[Lukey220]

Summit Racing has them (1409) in stock.

Mecruiser part number 805359T throttle bracket will work with the 1409 as the 2 bbl carb bracket will not. Makes a nice clean install of throttle bracket

Will I need to get an adapter plate if I go that route due to my intake being a spreadbore and edelbrock being squarebore?

 

[Scott06]

Will I need to get an adapter plate if I go that route due to my intake being a spreadbore and edelbrock being squarebore?

i believe so look on pg 2 of the install manual from edlebrock https://edelbrock-instructions-v1.s3.amazonaws.com/edelbrock/1409.pdf