new carburetor on 5.7L mercruiser alph-one not performaning like old

[bankermike]

replaced quarda jet 4bl carb on 91 ranger 5.7 litre with edelbrock mod.#1406 600 cfm square-flange, elec. choke, non-emission street performance carb. using an open adapter (not reccomended by edlebrock). realize this is an auto carb but q-jet appeared to be auto carb also (no j tubes). The new edelbrock runs great out of the water but does not have the power of old carb. Hole shot VERY SLOW & top end down from<br />55+ to -40 mph. checked linkage, new carb running at wide open. do I need new/bigger carb or can this carb be adjusted to perform like old one. new carb has several ports that Q-jet did'nt. edlebrock just does'nt seem to be getting enough gas to engine. could open adapter be the culprit or maybe additional vacuum ports? i'm stumped.

 

[tommays]

Re: new carburetor on 5.7L mercruiser alph-one not performaning like old

i think everybody will tell you the same thing there IS NO POINT IN DOING ANYTHING WITHOUT A MARINE CARB<br /> <br />tommays

 

[John_S]

Re: new carburetor on 5.7L mercruiser alph-one not performaning like old

You need a marine carb, for safety, and if you compare your 1406 to the edelbrock marine 1409, you will notice a differance in jets and rods. Assuming your spacer is a q-jet to square bore adapter, you are probably loosing some power there, as well.

 

[paulie0735]

Re: new carburetor on 5.7L mercruiser alph-one not performaning like old

Just need some more info to help you. What angle is your engine on? Is the new carb "new" or used? Why did you remove the q-jet? Check with Edelbrock re that adapter, it could be blocking a vacuum port in the base plate!

 

[Don S]

Re: new carburetor on 5.7L mercruiser alph-one not performaning like old

Maybe you need to watch this video before you work on your boat anymore.<br /><br />Reel Poor's Boom Video

 

[Bondo]

Re: new carburetor on 5.7L mercruiser alph-one not performaning like old

#1,......<br />

You need a marine carb, for safety, and if you compare your 1406 to the edelbrock marine 1409, you will notice a differance in jets and rods.<br />there IS NO POINT IN DOING ANYTHING WITHOUT A MARINE CARB

#2,........<br />

(not reccomended by edlebrock).

Until you get the Right Carb..............<br />And,.......<br />Learn to follow Instructions from people who Know,................<br /><br />There's Not much we can Do............<br /><br />Sorry Dude........

 

[bankermike]

Re: new carburetor on 5.7L mercruiser alph-one not performaning like old

Thanks for the replies. Pretty obvious I'm new to all of this. Paulie0735, not sur what you mean by angle of engine. The engine sits in boat as it would in an auto. new carb is in fact a brand new edel rock 1406. Carb. & adapter reccomened by "machanic" & parts store guy. Did'nt know open adapter not reccomended by edelbrock until too late. what's the difference between a marine carb & an auto carb? Mainly saftey or performance also? If marine carb is necessary, any reccomendations on replacement carb & best place to purchase. Anybody need a nearly new edelbrock 1406? Old Q-jet replaced due to corrosion caused by apparent water damage.<br />Thanks for your help!<br />learning the hard way!

 

[John_S]

Re: new carburetor on 5.7L mercruiser alph-one not performaning like old

What intake manifold do you have? I would assume it is the low-profile cast iron Q-jet manifold, if it is still stock. If that is the case, then the best bet would be a rebuilt marine q-jet, using the same jetting and rods as your old carb. Probably worth upgrading to electic choke, though. Holly also makes a marine 650cfm spreadbore. <br /><br />If you have the high-rise cast iron or most aftermarket aluminum, it will accept a square or spreadbore, without an adapter. Just may need a special gasket, etc. The Edelbrock 1409 is a 600/625cfm marine carb, that many have found to work well on 5.7L (search for posts), and easy to tune/adj and repair. There are Holly marine square bore carbs, but they are more expensive that the 1409 which is about $300 at discount automotive sources.

 

[bankermike]

Re: new carburetor on 5.7L mercruiser alph-one not performaning like old

everything is stock & original on the motor.

 

[Fishermark]

Re: new carburetor on 5.7L mercruiser alph-one not performaning like old

You can pick up a marine Edlebrock 1409 or 1410 (600 and 750 CFM respectively) at Summit for around $285 - $295.<br /><br />Here's a link: Summit Marine Carbs <br /><br />They also sell Holley, etc - all in marine versions.

 

[John_S]

Re: new carburetor on 5.7L mercruiser alph-one not performaning like old

<br />everything is stock & original on the motor.

If when you removed the carb, you saw four circles for the intake manifold carb base (2 small, 2 large) you have the cast iron 4brl low-rise. Unless you plan on replacing manifold, recommend staying with spreadbore carb. The Q-jet replacement will be the easiest and least costly, and require less adjustment. <br /><br />If you have two elongated ovals, with small seperation, you have the high rise version. The high rise came on the Mercruiser 350 mag. It will take both spread and square bore.

 

[jimmbo]

Re: new carburetor on 5.7L mercruiser alph-one not performaning like old

If the old carb was original the outside was probably painted black by Mercury during assenbly. Marine Q-jets don't have the J shape vent tube. at least I've never seen one on any units that were at my dealer. <br /><br />Holley did/maybe still makes a 650 spreadbore marine carb. I put one on my 5.7 Volvo and gained 5 mph over the original 500cfm Holley 2 bbl. Didn't even have to change manifolds cause Volvo put on a real nice high rise 4bbl and used an adapter to mount the 2bbl

 

[vrod2002]

Re: new carburetor on 5.7L mercruiser alph-one not performaning like old

I feel for you.I just went throught this with a 351 /volvo 72 monza. Get the 1409!Great carb. The guy I bought this boat from had also put a car vacuum advanced dist.on. Doesn't work.

 

[bankermike]

Re: new carburetor on 5.7L mercruiser alph-one not performaning like old

The 1409 is a square bore, right? Will still need adapter, right? Appears I have 4brl low rise manifold. I've read is prvious post that adapter is a horsepower theif. True? I'm not even sure what size my old Q-jet is. Was told 650. Will the 1409 deliver the same performance as my old q-jet or will I need a bigger carb? If I'm going to buy another new carb., I want to go ahead and get one that will deliver max performance, within reason $$, of course.

 

[John_S]

Re: new carburetor on 5.7L mercruiser alph-one not performaning like old

The old Q-jet was 750cfm, but the secondarys are vac, so only used what your engine needed. 350 mag engines used 750cfm Weber/Edelbrocks, again vac sec. 600cfm is all a 5.7L is going to need for the rpm range of 5K or less. <br /><br />You have a spreadbore, so use a spreadbore carb, ie Holly 650 spreadbore or Q-jet replacement. If you want to use a squarebore, change the manifold as well. Merc did use adapters, but it is a hp thief.