4.3 L carb question

[selmahotrod]

I have a 1995 18 ft runabout with the 4.3 GL. I just put a factory 4 bbl. intake and a new Holley marine 600 carb for this engine. I gained about 3 mph on top end but when accelerating for a dead stop with full throttle it does not want to take off very good. Is there a secondary adjustment I need to address? It has a manifold adapter on it - spreadbore to squarebore. Three fourths throttle is good. Any ideas?

 

[Don S]

Re: 4.3 L carb question

Did you adjust the idle mixture screws to the engine? They only come from the factory with a preliminary setting on them.

 

[selmahotrod]

Re: 4.3 L carb question

I did adjust the idle mixture screws. It idles perfect. Got me scratching my head.

 

[Don S]

Re: 4.3 L carb question

http://www.edelbrock.com/automotive_new/mc/carbs_acc/pdf/carb_owners_manual.pdf

 

[selmahotrod]

Re: 4.3 L carb question

This is a new Holley carb designed for a marine 4.3L. The linkeage hook up was perfect with this.

 

[Tail_Gunner]

Re: 4.3 L carb question

Tuning a engine

Timing set corectly
Plugs gapped correctly
Wires good
Rotor or cap not porous or cracked

Tuning a carb..black magic..

Is your acclerator pump linkage setup correctly...and secondaries opening right...600 cfm is a lot of carb on a older 4.3. Have you jetted correctly

Being sluggish out of the hole might point to much retardation on the timing....Quetion is it burning rich???

 

[selmahotrod]

Re: 4.3 L carb question

Everything new and everything adjusted properly.

 

[Don S]

Re: 4.3 L carb question

Everything new and everything adjusted properly.

Then nothing is wrong. I still say you haven't got the mixture right. A bit to rich or lean, and it will idle fine, but not take gas properly.
Not sure how I ended up giving you the Edelbrock link above, I know you said Holley.

 

[Tail_Gunner]

Re: 4.3 L carb question

Even though it is new does not mean it is jetted correctly. Eldebroks out of the box 600 cfm carb has a kit that needs to be installed to rejet and new needles...If i remeber right WCA Trim went thourgh a few jets to get where he wanted to be..Perhaps wh will chime in. I am not sure of your experience but a 95 4.3 was about a 170 hp motor and 600 cfm is a huge carb. You indicate your power is up @ wot where the engine gets a maxium air to fuel ratio which would help lean it out.

A 280 hp 4.3 uses a 600 cfm carb..good luck

Ahh the search function....I seriously doubt there can be a question that cant be answered with that funtion...

http://forums.iboats.com/showthread.php?t=50261&highlight=4.3+jetting


The Mercruiser 4.3 LX Weber settingsrimary Jet = 0.089Secondary Jet = 0.089Metering Rod = 16-6857 (68 x 57)Metering Rod Spring = YellowIf they are part of the kit, all the better.

There ya go...Call holley with those jet setting.....tell them what you have and i am sure they will recomend something

 

[selmahotrod]

Re: 4.3 L carb question

So you are thinking it is running to rich? Volvo offered this carb on this engine in 1995 at 570 CFM. I do not know what jet size they used.