1997 Mercruiser 5.7LX Bravo 3 Weber 9781S bogging

[tk1780]

My engine bogs when hitting full throttle out of the hole. It runs fine other than that. The carb has never been touched in 17 years but only 200 hrs.

I'm thinking about having the carb rebuilt ( or at least replacing the accelerator pump) or replacing the Weber with an Edelbrock 1410.

The rebuild is probably $200-250 and a new carb is $400.

My question is do I have to change the jets on the Edelbrock 1410 to match the jets on the Weber or is it plug and play? Also, any other tuning needed for the new 1410?

The jets on the Weber are Primary .098 and Secondary .092. The Edelbrock 1410 jets are Primary .113 and Secondary .107


Thanks,

 

[alldodge]

My engine bogs when hitting full throttle out of the hole. It runs fine other than that. The carb has never been touched in 17 years but only 200 hrs.

I'm thinking about having the carb rebuilt ( or at least replacing the accelerator pump) or replacing the Weber with an Edelbrock 1410.

The rebuild is probably $200-250 and a new carb is $400.

My question is do I have to change the jets on the Edelbrock 1410 to match the jets on the Weber or is it plug and play? Also, any other tuning needed for the new 1410?

The jets on the Weber are Primary .098 and Secondary .092. The Edelbrock 1410 jets are Primary .113 and Secondary .107


Thanks,

:welcome: to iboats

An expert will be along in a bit I hope with additional explanation, but I'll say this. The 1410 is a 750CFM carb which your 5.7 will never be able to pull in that much air. Your engine at WOT of 4800 RPM could possibility pull in 534CFM, so a better choice would be the 1409 which is 600CFM.
Jets pri .098 and sec .101

 

[tk1780]

Thanks for the reply. The Weber is a 750 CFM carb so I was trying to make a direct switch. Your logic is sound, but I guess I am assuming that the factory knew what they were doing when they put a 750 CFM carb on. Certainly the 1409 jet sizes are already closer to the original.

 

[sharkin95]

Here are some choices a rebuilt carb 9781s (3310 807262A) Allstate carbs $329.00 ... a rebuild kit $40-80.00... a Edelbrock #1409 for $370-$400 which will definetly work for your engine.If you have the Mag 350 5.7 LX and have a need for speed then stick with the 750 cfm Weber. If you don't have a need to pass everything but a gas station the #1409 or even the Weber 9665s primary jets .101 and second .095 will work.... Myself I would try a rebuild kit first either on e-bay or marinengines.com Your problem sounds like too rich of a mixture on the secondaries or a sticking accelerator pump.

 

[sharkin95]

Just so you know the Weber carbs run 80% of the time on the primaries thats why the primaries are bigger than the secondaries.When machanics change them they mostly change the metering rods and springs and not the jets..

 

[thumpar]

You could just buy a rebuild kit. They can be found for around $40.

 

[Bondo]

Ayuh,.... The Weber carb, is a carbon copy of the Edlebrock carbs,....

The parts, 'n pieces are direct interchange,....

They're a pretty simple carb,... I'd rebuild yer's before buyin' a New 1,.....

At the Edlebrock site, in the knowledge base, is a pdf. file that is the Bible for these Carter AFB Clones,....

 

[tk1780]

So are the extra CFM for top end performance or for low end as well?

I'm looking to boost low end.

 

[Bondo]

So are the extra CFM for top end performance or for low end as well?

I'm looking to boost low end.

Ayuh,.... A smaller carb runs smoother, with better low-end torque,.....

A Bigger carb allows it to breathe better, at top-end,....

 

[tk1780]

Thank you for your help!

 

[NHGuy]

That's why they use qjets. They have smaller primaries and vacuum actuated secondaries. When a quadrajet is wide open it only pulls the secondary air doors a little bit open on a 5.7. Hence the 650 cfm recommendation.
I can tell you that mine has great holeshot. The reason is, it has a good accelerator pump, and a reserve fuel well for the primary circuit that keeps the engine fed til the secondaries start to pull.
If it was me I'd redo the carb you have. But I'm a geek for anything complicated.
A lot of folks swear by the 1409's when new is needed.